Jorey Bump wrote, On 3/13/09 8:51 AM:
LuKreme wrote, at 03/13/2009 07:22 AM:
So I thought I'd see if anyone else thought that a helo in the form
[12.34.56.789] SHOULD be allowed. I mean, as far as I recall, this is
still technically allowed, right?
A bracketed IP address is valid in a HELO/EHLO, but is so rare in
legitimate mail that it's still worth blocking.
It should be noted that this is true only for mail transport, not mail
submission.
For the people still supporting the antiquated model of accepting mail
submission via SMTP rather than a proper port 587 daemon, it is important to
make allowances for the fact that MUA's frequently have no better choice
for their HELO argument than an IP literal, and sometimes even that is
pretty lousy (i.e. an ephemeral RFC1918 private IP)
