moore@betelgeuse.cs.utk.edu (Keith Moore) (12/05/89)
I've now seen several responses to my posted sendmail.cf fragment to
recognize a machine's domain literal without hard coding in the IP address.
Most of these were of the form (a) this won't work anyway, because some
vendors' sendmails don't support $[ and $], or (b) you shouldn't need
to do this because the resolver and DNS take away the need for domain literals,
and besides, you can always use telnet to talk to the machine's smtp server.
While I'm sure there are some versions of sendmail out there that don't
support $[ and $], I hope they are few in number. We have most of the
major brands of computers here (not just VAXen) at UTK, and $[ and $]
seem to work on all of them. If your particular machine doesn't support
this feature yet, be aware that your software is very out of date, and you
will indeed have to wire your IP address into your sendmail config somehow.
In response to (b), I'll try to be succinct:
1. Ability to recognize domain literals is required by the RFC 822 and
RFC 1123 specifications.
2. Even though they should not be used regularly, domain literals are
indeed useful.
3. The fact that many sites don't support domain literals on inbound mail
makes this otherwise useful feature unreliable.
4. For most machines running sendmail, they are easy to implement correctly.
With the hope that implementation of this part of the standard would
become more widespread, I posted a method of doing so that I believe to
be reasonably portable across most machines running UNIX and sendmail.
I've also tried to make people aware of the subtleties of using $[ and $]
with domain literals, and how things can fail if you're not careful.
If you prefer to implement this feature some other way, fine.
For those who believe that this feature should not be implemented, all I
can do is ask (along with the IETF) that you implement it anyway.
Keith Moore Internet: moore@cs.utk.edu
University of Tenn. CS Dept. BITNET: moore@utkvx
107 Ayres Hall, UT Campus UT Decnet: utkcs::moore
Knoxville Tennessee 37996-1301 Telephone: +1 615 974 0822