Path: utzoo!attcan!uunet!husc6!bloom-beacon!mit-eddie!uw-beaver!cornell!rochester!pt.cs.cmu.edu!andrew.cmu.edu!cfe+ From: cfe+@andrew.cmu.edu (Craig F. Everhart) Newsgroups: comp.mail.sendmail Subject: Re: Overlaying smail and mx-sendmail? Message-ID: Date: 13 Oct 88 18:27:28 GMT References: <8602@shamash.UUCP> <810@ncar.ucar.edu>, <12671@ncoast.UUCP> Organization: Carnegie Mellon Lines: 29 In-Reply-To: <12671@ncoast.UUCP> You're correct in that a temporary-failure result from the resolver should result in requeueing a piece of mail for a later delivery attempt, and this is indeed how things work when it's sendmail doing the resolver calls (e.g. looking for MX records or A records to do the actual connection). The only silly thing is in the $[ $] interface itself; all that happens is that sendmail makes an attempt to canonicalize the name. (The as-distributed version of the underlying C routine doesn't even return a success or failure code.) That is, there's no way that the person writing the sendmail.cf file (in which the $[ $] appear) can determine whether the resolver call succeeded or failed, and if it failed, whether it was a transient or permanent failure. The hack of adding the ``.'' and seeing if it stayed around is only an attempt to determine if the resolver call succeeded at all, and confounds the resolver's use of a sequence of ``default domain suffixes''. Nobody has yet invented a mechanism whereby the sendmail.cf program can query the result of the resolver call--except for perhaps the IDA sendmail kit. You might argue that sendmail should look at the result of the get-canonical-name routine and handle some of the failures itself; you could argue that if it were to get a temp failure on any $[ $]-spawned resolver call, that it should bypass sending to this addressee for now and move on to the next. Maybe that's reasonable. Is that what the existing sendmail.cf files/programs expect to happen? Should all $[$] requests be assured of working before trying the first delivery? (What happens if a partially-qualified domain name escapes *your* site?) How should sendmail deal with permanent failures--by rejecting the address as invalid? Hardly. Might there be an answer to all these questions? Craig Everhart Andrew message system