a) If we are using SMTPD we make it easier for developers to deal with incoming email. This is because they do not have to collect the emails from the mailbox folder and process them in a scheduled proc, but right upon delivery you can start off a callback
b) The users do not have to concern themselves with "how do i setup my mailserver so OpenACS gets incoming emails"
c) If all email is handled by this email server we can pretty much disregard anything immediately and setup "root@.." to be forwarded to the system owner (in the case you have a system purely for OpenACS, which is not so uncommon)
So not something large achieveable, but just taking a couple of headaches of people.
