[IMail Forum] Accepting/Denying SMTP connections

[Jeff Andreou]

We are currently setup to "relay for addresses" with only a small set of trusted ips on our mail server network.  The current desired implementation is that the iMail box be used for pop3 and some authenticated clients SMTP with another SMTP server running Exim acting as a mail gateway to the outside world.  The problem that we're seeing is that some messages are doing an end-run around the Exim box and sending directly to the iMail box despite the fact that there are no mx records that point to the iMail box.  There is, however, an 'a' record.  The messages that are getting around the Exim box are coming from ip addresses that are not listed in the "relay for" settings.  Given that we still want to allow certain machines and users on the specified networks to use iMail for SMTP, is there a way to configure the iMail box so that it does not accept any SMTP connections unless they come from the specified network or are authenticated via SMTP AUTH?

Something I just noticed in the documentation; I see that iMail will accept any SMTP connections that either originate from those ip's or are destined for addresses on those ip's.  Would this be a simple matter of excluding the iMail box's ip from the accepted range?  Are there any unforeseen consequences that I should know about before excluding that ip, like screwing up internal mail delivery or locally generated bounce messages?