# # This file is best read with ``perldoc plugins.pod'' # ### # Conventions: # plugin names: F, F # constants: I # smtp commands, answers: B, B<250 Queued!> # # Notes: # * due to restrictions of some POD parsers, no C<<$object->method()>> # are allowed, use C<$object-Emethod()> # =head1 Introduction Plugins are the heart of qpsmtpd. The core implements only basic SMTP protocol functionality. No useful function can be done by qpsmtpd without loading plugins. Plugins are loaded on startup where each of them register their interest in various I provided by the qpsmtpd core engine. At least one plugin B allow or deny the B command to enable receiving mail. The F plugin is the standard plugin for this. Other plugins provide extra functionality related to this; for example the F plugin. =head2 Loading Plugins The list of plugins to load are configured in the I configuration file. One plugin per line, empty lines and lines starting with I<#> are ignored. The order they are loaded is the same as given in this config file. This is also the order the registered I are run. The plugins are loaded from the F directory or from a subdirectory of it. If a plugin should be loaded from such a subdirectory, the directory must also be given, like the F in the example below. Alternate plugin directories may be given in the F config file, one directory per line, these will be searched first before using the builtin fallback of F relative to the qpsmtpd root directory. It may be necessary, that the F must be used (if you're using F, for example). Some plugins may be configured by passing arguments in the F config file. A plugin can be loaded two or more times with different arguments by adding I<:N> to the plugin filename, with I being a number, usually starting at I<0>. Another method to load a plugin is to create a valid perl module, drop this module in perl's C<@INC> path and give the name of this module as plugin name. The only restriction to this is, that the module name B contain I<::>, e.g. C would be ok, C not. Appending of I<:0>, I<:1>, ... does not work with module plugins. check_relay virus/clamdscan spamassassin reject_threshold 7 my_rcpt_check example.com my_rcpt_check:0 example.org My::Plugin =head1 Anatomy of a plugin A plugin has at least one method, which inherits from the C object. The first argument for this method is always the plugin object itself (and usually called C<$self>). The most simple plugin has one method with a predefined name which just returns one constant. # plugin temp_disable_connection sub hook_connect { return(DENYSOFT, "Sorry, server is temporarily unavailable."); } While this is a valid plugin, it is not very useful except for rare circumstances. So let us see what happens when a plugin is loaded. =head2 Initialisation After the plugin is loaded the C method of the plugin is called, if present. The arguments passed to C are =over 4 =item $self the current plugin object, usually called C<$self> =item $qp the Qpsmtpd object, usually called C<$qp>. =item @args the values following the plugin name in the F config, split by white space. These arguments can be used to configure the plugin with default and/or static config settings, like database paths, timeouts, ... =back This is mainly used for inheriting from other plugins, but may be used to do the same as in C. The next step is to register the hooks the plugin provides. Any method which is named C is automagically added. Plugins should be written using standard named hook subroutines. This allows them to be overloaded and extended easily. Because some of the callback names have characters invalid in subroutine names , they must be translated. The current translation routine is C. If you choose not to use the default naming convention, you need to register the hooks in your plugin in the C method (see below) with the C call on the plugin object. sub register { my ($self, $qp, @args) = @_; $self->register_hook("mail", "mail_handler"); $self->register_hook("rcpt", "rcpt_handler"); } sub mail_handler { ... } sub rcpt_handler { ... } The C method is called last. It receives the same arguments as C. There is no restriction, what you can do in C, but creating database connections and reuse them later in the process may not be a good idea. This initialisation happens before any C is done. Therefore the file handle will be shared by all qpsmtpd processes and the database will probably be confused if several different queries arrive on the same file handle at the same time (and you may get the wrong answer, if any). This is also true for F and the pperl flavours, but not for F started by (x)inetd or tcpserver. In short: don't do it if you want to write portable plugins. =head2 Inheritance Inheriting methods from other plugins is an advanced topic. You can alter arguments for the underlying plugin, prepare something for the I plugin or skip a hook with this. Instead of modifying C<@ISA> directly in your plugin, use the C method from the C subroutine. # rcpt_ok_child sub init { my ($self, $qp, @args) = @_; $self->isa_plugin("rcpt_ok"); } sub hook_rcpt { my ($self, $transaction, $recipient) = @_; # do something special here... $self->SUPER::hook_rcpt($transaction, $recipient); } =head2 Config files Most of the existing plugins fetch their configuration data from files in the F sub directory. This data is read at runtime and may be changed without restarting qpsmtpd. B<(FIXME: caching?!)> The contents of the files can be fetched via @lines = $self->qp->config("my_config"); All empty lines and lines starting with C<#> are ignored. If you don't want to read your data from files, but from a database you can still use this syntax and write another plugin hooking the C hook. =head2 Logging Log messages can be written to the log file (or STDERR if you use the F plugin) with $self->qp->log($loglevel, $logmessage); The log level is one of (from low to high priority) =over 4 =item LOGDEBUG =item LOGINFO =item LOGNOTICE =item LOGWARN =item LOGERROR =item LOGCRIT =item LOGALERT =item LOGEMERG =back While debugging your plugins, you want to set the log level in the F config file to I. This will log very much data. To restrict this output just to the plugin you are debugging, you can use the following plugin: =cut FIXME: Test if this really works as inteded ;-) =pod # logging/debug_plugin - just show LOGDEBUG messages of one plugin # Usage: # logging/debug_plugin my_plugin LOGLEVEL # # LOGLEVEL is the log level for all other log messages use Qpsmtpd::Constants; sub register { my ($self, $qp, $plugin, $loglevel) = @_; die "no plugin name given" unless $plugin; $loglevel = "LOGWARN" unless defined $loglevel; $self->{_plugin} = $plugin; $self->{_level} = Qpsmtpd::Constants::log_level($loglevel); $self->{_level} = LOGWARN unless defined $self->{_level}; } sub hook_logging { my ($self, $transaction, $trace, $hook, $plugin, @log) = @_; return(OK) # drop these lines if $plugin ne $self->{_plugin} and $trace > $self->{_level}; return(DECLINED); } The above plugin should be loaded before the default logging plugin, which logs with I. The plugin name must be the one returned by the C method of the debugged plugin. This is probably not the same as the name of the plugin (i.e. not the same you write in the F config file). In doubt: take a look in the log file for lines like C (here: F =E F). =head2 Information about the current plugin Each plugin inherits the public methods from C. =over 4 =item plugin_name() Returns the name of the currently running plugin =item hook_name() Returns the name of the running hook =item auth_user() Returns the name of the user the client is authed as (if authentication is used, of course) =item auth_mechanism() Returns the auth mechanism if authentication is used =item connection() Returns the C object associated with the current connection =item transaction() Returns the C object associated with the current transaction =back =head2 Temporary Files The temporary file and directory functions can be used for plugin specific workfiles and will automatically be deleted at the end of the current transaction. =over 4 =item temp_file() Returns a unique name of a file located in the default spool directory, but does not open that file (i.e. it is the name not a file handle). =item temp_dir() Returns the name of a unique directory located in the default spool directory, after creating the directory with 0700 rights. If you need a directory with different rights (say for an antivirus daemon), you will need to use the base function C<$self-Eqp-Etemp_dir()>, which takes a single parameter for the permissions requested (see L for details). A directory created like this will not be deleted when the transaction is ended. =item spool_dir() Returns the configured system-wide spool directory. =back =head2 Connection and Transaction Notes Both may be used to share notes across plugins and/or hooks. The only real difference is their life time. The connection notes start when a new connection is made and end, when the connection ends. This can, for example, be used to count the number of none SMTP commands. The plugin which uses this is the F plugin from the qpsmtpd core distribution. The transaction note starts after the B command and are just valid for the current transaction, see below in the I hook when the transaction ends. =head1 Return codes Each plugin must return an allowed constant for the hook and (usually) optionally a ``message'' for the client. Generally all plugins for a hook are processed until one returns something other than I. Plugins are run in the order they are listed in the F configuration file. The return constants are defined in C and have the following meanings: =over 4 =item DECLINED Plugin declined work; proceed as usual. This return code is I unless noted otherwise. =item OK Action allowed. =item DENY Action denied. =item DENYSOFT Action denied; return a temporary rejection code (say B<450> instead of B<550>). =item DENY_DISCONNECT Action denied; return a permanent rejection code and disconnect the client. Use this for "rude" clients. Note that you're not supposed to do this according to the SMTP specs, but bad clients don't listen sometimes. =item DENYSOFT_DISCONNECT Action denied; return a temporary rejection code and disconnect the client. See note above about SMTP specs. =item DONE Finishing processing of the request. Usually used when the plugin sent the response to the client. =back The I constant is not mentioned here, because it is not used by plugins directly. =head1 SMTP hooks This section covers the hooks, which are run in a normal SMTP connection. The order of these hooks is like you will (probably) see them, while a mail is received. Every hook receives a C object of the currently running plugin as the first argument. A C object is the second argument of the current transaction in the most hooks, exceptions are noted in the description of the hook. If you need examples how the hook can be used, see the source of the plugins, which are given as example plugins. =head2 hook_pre_connection Called by a controlling process (e.g. forkserver or prefork) after accepting the remote server, but before beginning a new instance (or handing the connection to the worker process). Useful for load-management and rereading large config files at some frequency less than once per session. This hook only works in the F and F flavours. =cut NOT FOR: -async, apache, -server and inetd/pperl =pod B You should not use this hook to do major work and / or use lookup methods which (I) take some time, like DNS lookups. This will slow down B incoming connections, no other connection will be accepted while this hook is running! Arguments this hook receives are: my ($self,$transaction,%args) = @_; # %args is: # %args = ( remote_ip => inet_ntoa($iaddr), # remote_port => $port, # local_ip => inet_ntoa($laddr), # local_port => $lport, # max_conn_ip => $MAXCONNIP, # child_addrs => [values %childstatus], # ); B the C<$transaction> is of course C at this time. Allowed return codes are =over 4 =item DENY / DENY_DISCONNECT returns a B<550> to the client and ends the connection =item DENYSOFT / DENYSOFT_DISCONNECT returns a B<451> to the client and ends the connection =back Anything else is ignored. Example plugins are F and F. =head2 hook_connect It is called at the start of a connection before the greeting is sent to the connecting client. Arguments for this hook are my $self = shift; B in fact you get passed two more arguments, which are C at this early stage of the connection, so ignore them. Allowed return codes are =over 4 =item OK Stop processing plugins, give the default response =item DECLINED Process the next plugin =item DONE Stop processing plugins and dont give the default response, i.e. the plugin gave the response =item DENY Return hard failure code and disconnect =item DENYSOFT Return soft failure code and disconnect =back Example plugin for this hook is the F plugin. =head2 hook_helo / hook_ehlo It is called after the client sent B (hook_ehlo) or B (hook_helo) Allowed return codes are =over 4 =item DENY Return a 550 code =item DENYSOFT Return a B<450> code =item DENY_DISCONNECT / DENYSOFT_DISCONNECT as above but with disconnect =item DONE Qpsmtpd wont do anything, the plugin sent the message =item DECLINED Qpsmtpd will send the standard B/B answer, of course only if all plugins hooking I return I. =back Arguments of this hook are my ($self, $transaction, $host) = @_; # $host: the name the client sent in the # (EH|HE)LO line B C<$transaction> is C at this point. =head2 hook_mail_pre After the B line sent by the client is broken into pieces by the C, this hook recieves the results. This hook may be used to pre-accept adresses without the surrounding IE> (by adding them) or addresses like Iuser@example.com.E> or Iuser@example.com E> by removing the trailing I<"."> / C<" ">. Expected return values are I and an address which must be parseable by Cparse()> on success or any other constant to indicate failure. Arguments are my ($self, $transaction, $addr) = @_; =head2 hook_mail Called right after the envelope sender line is parsed (the B command). The plugin gets passed a C object, which means the parsing and verifying the syntax of the address (and just the syntax, no other checks) is already done. Default is to allow the sender address. The remaining arguments are the extensions defined in RFC 1869 (if sent by the client). B According to the SMTP protocol, you can not reject an invalid sender until after the B stage (except for protocol errors, i.e. syntax errors in address). So store it in an C<$transaction-Enote()> and process it later in an rcpt hook. Allowed return codes are =over 4 =item OK sender allowed =item DENY Return a hard failure code =item DENYSOFT Return a soft failure code =item DENY_DISCONNECT / DENYSOFT_DISCONNECT as above but with disconnect =item DECLINED next plugin (if any) =item DONE skip further processing, plugin sent response =back Arguments for this hook are my ($self,$transaction, $sender, %args) = @_; # $sender: an Qpsmtpd::Address object for # sender of the message Example plugins for the C are F and F. =head2 hook_rcpt_pre See C, s/MAIL FROM:/RCPT TO:/. =head2 hook_rcpt This hook is called after the client sent an I command (after parsing the line). The given argument is parsed by C, then this hook is called. Default is to deny the mail with a soft error code. The remaining arguments are the extensions defined in RFC 1869 (if sent by the client). Allowed return codes =over 4 =item OK recipient allowed =item DENY Return a hard failure code, for example for an I message. =item DENYSOFT Return a soft failure code, for example if the connect to a user lookup database failed =item DENY_DISCONNECT / DENYSOFT_DISCONNECT as above but with disconnect =item DONE skip further processing, plugin sent response =back Arguments are my ($self, $transaction, $recipient, %args) = @_; # $rcpt = Qpsmtpd::Address object with # the given recipient address Example plugin is F. =head2 hook_data After the client sent the B command, before any data of the message was sent, this hook is called. B This hook, like B, B, B, B, is an endpoint of a pipelined command group (see RFC 1854) and may be used to detect ``early talkers''. Since svn revision 758 the F plugin may be configured to check at this hook for ``early talkers''. Allowed return codes are =over 4 =item DENY Return a hard failure code =item DENYSOFT Return a soft failure code =item DENY_DISCONNECT / DENYSOFT_DISCONNECT as above but with disconnect =item DONE Plugin took care of receiving data and calling the queue (not recommended) B The only real use for I is implementing other ways of receiving the message, than the default... for example the CHUNKING SMTP extension (RFC 1869, 1830/3030) ... a plugin for this exists at http://svn.perl.org/qpsmtpd/contrib/vetinari/experimental/chunking, but it was never tested ``in the wild''. =back Arguments: my ($self, $transaction) = @_; Example plugin is F. =head2 hook_received_line If you wish to provide your own Received header line, do it here. You can use or discard any of the given arguments (see below). Allowed return codes: =over 4 =item OK, $string use this string for the Received header. =item anything else use the default Received header =back Arguments are my ($self, $transaction, $smtp, $auth, $sslinfo) = @_; # $smtp - the SMTP type used (e.g. "SMTP" or "ESMTP"). # $auth - the Auth header additionals. # $sslinfo - information about SSL for the header. =head2 hook_data_post The C hook is called after the client sent the final C<.\r\n> of a message, before the mail is sent to the queue. Allowed return codes are =over 4 =item DENY Return a hard failure code =item DENYSOFT Return a soft failure code =item DENY_DISCONNECT / DENYSOFT_DISCONNECT as above but with disconnect =item DONE skip further processing (message will not be queued), plugin gave the response. B just returning I from a special queue plugin does (nearly) the same (i.e. dropping the mail to F) and you don't have to send the response on your own. If you want the mail to be queued, you have to queue it manually! =back Arguments: my ($self, $transaction) = @_; Example plugins: F, F =head2 hook_queue_pre This hook is run, just before the mail is queued to the ``backend''. You may modify the in-process transaction object (e.g. adding headers) or add something like a footer to the mail (the latter is not recommended). Allowed return codes are =over 4 =item DONE no queuing is done =item OK / DECLINED queue the mail =back =head2 hook_queue When all C hooks accepted the message, this hook is called. It is used to queue the message to the ``backend''. Allowed return codes: =over 4 =item DONE skip further processing (plugin gave response code) =item OK Return success message, i.e. tell the client the message was queued (this may be used to drop the message silently). =item DENY Return hard failure code =item DENYSOFT Return soft failure code, i.e. if disk full or other temporary queuing problems =back Arguments: my ($self, $transaction) = @_; Example plugins: all F plugins =head2 hook_queue_post This hook is called always after C. If the return code is B I, a message (all remaining return values) with level I is written to the log. Arguments are my $self = shift; B C<$transaction> is not valid at this point, therefore not mentioned. =head2 hook_reset_transaction This hook will be called several times. At the beginning of a transaction (i.e. when the client sends a B command the first time), after queueing the mail and every time a client sends a B command. Arguments are my ($self, $transaction) = @_; B don't rely on C<$transaction> being valid at this point. =head2 hook_quit After the client sent a B command, this hook is called (before the C). Allowed return codes =over 4 =item DONE plugin sent response =item DECLINED next plugin and / or qpsmtpd sends response =back Arguments: the only argument is C<$self> =cut ### XXX: FIXME pass the rest of the line to this hook? =pod Expample plugin is the F plugin. =head2 hook_disconnect This hook will be called from several places: After a plugin returned I, before connection is disconnected or after the client sent the B command, AFTER the quit hook and ONLY if no plugin hooking C returned I. All return values are ignored, arguments are just C<$self> Example plugin is F =head2 hook_post_connection This is the counter part of the C hook, it is called directly before the connection is finished, for example, just before the qpsmtpd-forkserver instance exits or if the client drops the connection without notice (without a B). This hook is not called if the qpsmtpd instance is killed. =cut FIXME: we should run this hook on a ``SIGHUP'' or some other signal? =pod B This hook only works in the (x)inetd, -forkserver and -prefork flavours. The only argument is C<$self> and all return codes are ignored, it would be too late anyway :-). Example: F =head1 Parsing Hooks Before the line from the client is parsed by Cparse()> with the built in parser, these hooks are called. They can be used to supply a parsing function for the line, which will be used instead of the built in parser. The hook must return two arguments, the first is (currently) ignored, the second argument must be a (CODE) reference to a sub routine. This sub routine receives three arguments: =over 4 =item $self the plugin object =item $cmd the command (i.e. the first word of the line) sent by the client =item $line the line sent by the client without the first word =back Expected return values from this sub are I and a reason which is sent to the client or I and the C<$line> broken into pieces according to the syntax rules for the command. B, the C hook was never implemented,...> =head2 hook_helo_parse / hook_ehlo_parse The provided sub routine must return two or more values. The first is discarded, the second is the hostname (sent by the client as argument to the B / B command). All other values are passed to the helo / ehlo hook. This hook may be used to change the hostname the client sent... not recommended, but if your local policy says only to accept I hosts with FQDNs and you have a legal client which can not be changed to send his FQDN, this is the right place. =head2 hook_mail_parse / hook_rcpt_parse The provided sub routine must return two or more values. The first is either I to indicate that parsing of the line was successfull or anything else to bail out with I<501 Syntax error in command>. In case of failure the second argument is used as the error message for the client. If parsing was successfull, the second argument is the sender's / recipient's address (this may be without the surrounding I> and I>, don't add them here, use the C / C methods for this). All other arguments are sent to the C hook as B / B parameters (see RFC 1869 I for more info). Note that the mail and rcpt hooks expect a list of key/value pairs as the last arguments. =head2 hook_auth_parse B =head1 Special hooks Now some special hooks follow. Some of these hooks are some internal hooks, which may be used to alter the logging or retrieving config values from other sources (other than flat files) like SQL databases. =head2 hook_logging This hook is called when a log message is written, for example in a plugin it fires if someone calls C<$self-Elog($level, $msg);>. Allowed return codes are =over 4 =item DECLINED next logging plugin =item OK (not I, as some might expect!) ok, plugin logged the message =back Arguments are my ($self, $transaction, $trace, $hook, $plugin, @log) = @_; # $trace: level of message, for example # LOGWARN, LOGDEBUG, ... # $hook: the hook in\/for which this logging # was called # $plugin: the plugin calling this hook # @log: the log message B C<$transaction> may be C, depending when / where this hook is called. It's probably best not to try acessing it. All F plugins can be used as example plugins. =head2 hook_deny This hook is called after a plugin returned I, I, I or I. All return codes are ignored, arguments are my ($self, $transaction, $prev_hook, $return, $return_text) = @_; B C<$transaction> may be C, depending when / where this hook is called. It's probably best not to try acessing it. Example plugin for this hook is F. =head2 hook_ok The counter part of C, it is called after a plugin B return I, I, I or I. All return codes are ignored, arguments are my ( $self, $transaction, $prev_hook, $return, $return_text ) = @_; B C<$transaction> may be C, depending when / where this hook is called. It's probably best not to try acessing it. =head2 hook_config Called when a config file is requested, for example in a plugin it fires if someone calls Cqp-Econfig($cfg_name);>. Allowed return codes are =over 4 =item DECLINED plugin didn't find the requested value =item OK requested values as C<@list>, example: return (OK, @{$config{$value}}) if exists $config{$value}; return (DECLINED); =back Arguments: my ($self,$transaction,$value) = @_; # $value: the requested config item(s) B C<$transaction> may be C, depending when / where this hook is called. It's probably best not to try acessing it. Example plugin is F from the qpsmtpd distribution. =head2 hook_unrecognized_command This is called if the client sent a command unknown to the core of qpsmtpd. This can be used to implement new SMTP commands or just count the number of unknown commands from the client, see below for examples. Allowed return codes: =over 4 =item DENY_DISCONNECT Return B<521> and disconnect the client =item DENY Return B<500> =item DONE Qpsmtpd wont do anything; the plugin responded, this is what you want to return, if you are implementing new commands =item Anything else... Return B<500 Unrecognized command> =back Arguments: my ($self, $transaction, $cmd, @args) = @_; # $cmd = the first "word" of the line # sent by the client # @args = all the other "words" of the # line sent by the client # "word(s)": white space split() line B C<$transaction> may be C, depending when / where this hook is called. It's probably best not to try acessing it. Example plugin is F. =head2 hook_vrfy If the client sents the B command, this hook is called. Default is to return a message telling the user to just try sending the message. Allowed return codes: =over 4 =item OK Recipient Exists =item DENY Return a hard failure code =item DONE Return nothing and move on =item Anything Else... Return a B<252> =back Arguments are: my ($self) = shift; =cut FIXME: this sould be changed in Qpsmtpd::SMTP to pass the rest of the line as arguments to the hook =pod =head2 hook_post_fork B This hook is only available in qpsmtpd-async. It is called while starting qpsmtpd-async. You can run more than one instance of qpsmtpd-async (one per CPU probably). This hook is called after forking one instance. Arguments: my $self = shift; The return values of this hook are discarded. =head1 Authentication hooks =cut B auth_parse #=head2 auth B #=head2 auth-plain B #=head2 auth-login B #=head2 auth-cram-md5 B =pod ...documentation will follow later =head1 Writing your own plugins This is a walk through a new queue plugin, which queues the mail to a (remote) QMQP-Server. First step is to pull in the necessary modules use IO::Socket; use Text::Netstring qw( netstring_encode netstring_decode netstring_verify netstring_read ); We know, we need a server to send the mails to. This will be the same for every mail, so we can use arguments to the plugin to configure this server (and port). Inserting this static config is done in C: sub register { my ($self, $qp, @args) = @_; die "No QMQP server specified in qmqp-forward config" unless @args; $self->{_qmqp_timeout} = 120; if ($args[0] =~ /^([\.\w_-]+)$/) { $self->{_qmqp_server} = $1; } else { die "Bad data in qmqp server: $args[0]"; } $self->{_qmqp_port} = 628; if (@args > 1 and $args[1] =~ /^(\d+)$/) { $self->{_qmqp_port} = $1; } $self->log(LOGWARN, "WARNING: Ignoring additional arguments.") if (@args > 2); } We're going to write a queue plugin, so we need to hook to the I hook. sub hook_queue { my ($self, $transaction) = @_; $self->log(LOGINFO, "forwarding to $self->{_qmqp_server}:" ."$self->{_qmqp_port}"); The first step is to open a connection to the remote server. my $sock = IO::Socket::INET->new( PeerAddr => $self->{_qmqp_server}, PeerPort => $self->{_qmqp_port}, Timeout => $self->{_qmqp_timeout}, Proto => 'tcp') or $self->log(LOGERROR, "Failed to connect to " ."$self->{_qmqp_server}:" ."$self->{_qmqp_port}: $!"), return(DECLINED); $sock->autoflush(1); =over 4 =item * The client starts with a safe 8-bit text message. It encodes the message as the byte string C. (The last line is usually, but not necessarily, empty.) The client then encodes this byte string as a netstring. The client also encodes the envelope sender address as a netstring, and encodes each envelope recipient address as a netstring. The client concatenates all these netstrings, encodes the concatenation as a netstring, and sends the result. (from L) =back The first idea is to build the package we send, in the order described in the paragraph above: my $message = $transaction->header->as_string; $transaction->body_resetpos; while (my $line = $transaction->body_getline) { $message .= $line; } $message = netstring_encode($message); $message .= netstring_encode($transaction->sender->address); for ($transaction->recipients) { push @rcpt, $_->address; } $message .= join "", netstring_encode(@rcpt); print $sock netstring_encode($message) or do { my $err = $!; $self->_disconnect($sock); return(DECLINED, "Failed to print to socket: $err"); }; This would mean, we have to hold the full message in memory... Not good for large messages, and probably even slower (for large messages). Luckily it's easy to build a netstring without the help of the C module if you know the size of the string (for more info about netstrings see L). We start with the sender and recipient addresses: my ($addrs, $headers, @rcpt); $addrs = netstring_encode($transaction->sender->address); for ($transaction->recipients) { push @rcpt, $_->address; } $addrs .= join "", netstring_encode(@rcpt); Ok, we got the sender and the recipients, now let's see what size the message is. $headers = $transaction->header->as_string; my $msglen = length($headers) + $transaction->body_length; We've got everything we need. Now build the netstrings for the full package and the message. First the beginning of the netstring of the full package # (+ 2: the ":" and "," of the message's netstring) print $sock ($msglen + length($msglen) + 2 + length($addrs)) .":" ."$msglen:$headers" ### beginning of messages netstring or do { my $err = $!; $self->_disconnect($sock); return(DECLINED, "Failed to print to socket: $err"); }; Go to beginning of the body $transaction->body_resetpos; If the message is spooled to disk, read the message in blocks and write them to the server if ($transaction->body_fh) { my $buff; my $size = read $transaction->body_fh, $buff, 4096; unless (defined $size) { my $err = $!; $self->_disconnect($sock); return(DECLINED, "Failed to read from body_fh: $err"); } while ($size) { print $sock $buff or do { my $err = $!; $self->_disconnect($sock); return(DECLINED, "Failed to print to socket: $err"); }; $size = read $transaction->body_fh, $buff, 4096; unless (defined $size) { my $err = $!; $self->_disconnect($sock); return(DECLINED, "Failed to read from body_fh: $err"); } } } Else we have to read it line by line ... else { while (my $line = $transaction->body_getline) { print $sock $line or do { my $err = $!; $self->_disconnect($sock); return(DECLINED, "Failed to print to socket: $err"); }; } } Message is at the server, now finish the package. print $sock "," # end of messages netstring .$addrs # sender + recpients ."," # end of netstring of # the full package or do { my $err = $!; $self->_disconnect($sock); return(DECLINED, "Failed to print to socket: $err"); }; We're done. Now let's see what the remote qmqpd says... =over 4 =item * (continued from L:) The server's response is a nonempty string of 8-bit bytes, encoded as a netstring. The first byte of the string is either K, Z, or D. K means that the message has been accepted for delivery to all envelope recipients. This is morally equivalent to the 250 response to DATA in SMTP; it is subject to the reliability requirements of RFC 1123, section 5.3.3. Z means temporary failure; the client should try again later. D means permanent failure. Note that there is only one response for the entire message; the server cannot accept some recipients while rejecting others. =back my $answer = netstring_read($sock); $self->_disconnect($sock); if (defined $answer and netstring_verify($answer)) { $answer = netstring_decode($answer); $answer =~ s/^K// and return(OK, "Queued! $answer"); $answer =~ s/^Z// and return(DENYSOFT, "Deferred: $answer"); $answer =~ s/^D// and return(DENY, "Denied: $answer"); } If this is the only F plugin, the client will get a 451 temp error: return(DECLINED, "Protocol error"); } sub _disconnect { my ($self,$sock) = @_; if (defined $sock) { eval { close $sock; }; undef $sock; } } =head1 Advanced Playground =head2 Discarding messages If you want to make the client think a message has been regularily accepted, but in real you delete it or send it to F, ..., use something like the following plugin and load it before your default queue plugin. sub hook_queue { my ($self, $transaction) = @_; if ($transaction->notes('discard_mail')) { my $msg_id = $transaction->header->get('Message-Id') || ''; $msg_id =~ s/[\r\n].*//s; return(OK, "Queued! $msg_id"); } return(DECLINED); } =head2 TBC... :-) =cut # vim: ts=2 sw=2 expandtab