> It's a SMTP protocol frontend for httpd. It will have the power to be a > sendmail replacer or to supply content via SMTP because it will delegate > most of the actual handling to other modules. All the details haven't > been worked out yet, but it will make use of the Apache 2.x filters and > handlers. For Instance: > > [core] -> [mod_smtpd] -> [mod_insert_special_use_mail_handler] > a setup like that could be used, but let's say you want to filter out > junk mail. Use an input filter! > > [core] -> [mod_smtpd] -> [mod_junk_mail_filter] -> [mod_other_thing]
Just to give an idea of the added flexibility of SMTP support within an httpd module; if we were just using pipes to/from sendmail then you have very limited information - basically just the mail data after receipt and no ability to talk back to the peer during the mail transaction. This is the problem encountered by many spam filters, as to be most effective they really need to be _involved_ in the SMTP transaction and not just stage 2, after receipt happens. Think greylisting as an example. Also, since mod_smtpd will receive emails from MTAs itself, and prepare its own data structures for passing on the data to other modules, this means that it can pass along useful information that are difficult or impossible to determine from just message headers/body. For example, IP address of the incoming or outgoing relay, helo/intro identification of peer, protocol violations or warnings, connection data rate perhaps... brainstorming.
