PMDF System Manager's Guide

PMDF often receives from misconfigured or incompliant mailers and SMTP clients addresses which do not contain a domain name. PMDF, showing at least some respect for standards, must attempt to make such addresses legal before allowing them to pass further. PMDF does this by appending a domain name to the address (e.g., appends "@example.com" to "mrochek"). For envelope To: addresses missing a domain name, PMDF always assumes that the local host name should be appended. However for other addresses, such as From: addresses, in the case of the PMDF SMTP server there are at least two reasonable choices for the domain name: the local PMDF host name and the remote host name reported by the client SMTP. Or in some cases, there may be yet a third reasonable choice---a particular domain name to add to messages coming in that channel. Now, either of these two first choices are likely to be correct as both may occur operationally with some frequency. The use of the remote host's domain name is appropriate when dealing with improperly configured SMTP clients. The use of the local host's domain name may be appropriate when dealing with a lightweight remote mail client such as a POP or IMAP client that uses SMTP to post messages. Or if lightweight remote mail clients such as POP or IMAP clients "ought" to have their own specific domain name which is not that of the local host, then adding that specific other domain name may be appropriate. The best that PMDF can do is to allow the choice to be made on a channel by channel basis.

The remotehost channel keyword specifies that the remote host's name should be used. The noremotehost channel keyword specifies that the local host's name should be used. noremotehost is the default.

The defaulthost channel keyword is used to specify a particular host name to append to incoming bare usernames; it must to be followed by the domain name to use in completing addresses coming in that channel. nodefaulthost is the default.

Note that the switchchannel keyword described above can be used to associated incoming SMTP connections with a particular channel. This facility can be used to group remote mail clients on a channel where they will receive proper treatment. Alternatively, it is an unconditionally simpler proposition to deploy standards-compliant remote mail clients (even if a multitude of incompliant clients are in use) rather than attempting to fix the network-wide problem on your PMDF hosts.