>In the past, I have seen AOL drop mail if the reverse DNS does not reslove
>to the domain in question. It seems you are hosted by twinstar and if the
>AOL mailserver does a reverse DNS lookup and it resolves to Twinstar it may
>beleive it is spam and drop it with no reply.
Just a quick clarification about reverse DNS lookups. There are several
ways that a mail server can drop (or do other unwanted stuff to) mail based
on reverse DNS entries:
[1] Drop the mail if there is no reverse DNS entry. This is rare, but
rumor has it that AOL did/does this.
[2] Drop the mail if the reverse DNS entry doesn't exist, or if it exists
but doesn't match the host name in the SMTP banner. No mail servers that I
know of do this, which is a good thing, because they wouldn't receive mail
from any IMail server (IMail incorrectly reports "X1" as the host name).
[3] Drop the mail if the reverse DNS doesn't exist, or it does exist but
doesn't match one of several other things (such as the MAIL FROM:
domain). This almost certainly isn't used, as it wouldn't let you use
virtual domains.
[4] Drop the mail if there is no reverse DNS entry, or if it exists but
doesn't have a corresponding A record (IE reverse DNS for 127.0.0.1 is
"1.0.0.127.in-addr.arpa" or "localhost", neither of which has an A
record). This is similar to #1.
So the key is simply to make sure that you have a reverse DNS entry set up
for the IP address of the mail server (the RFCs require this of all hosts,
but the majority of hosts don't have the reverse DNS entry). You don't
have to worry about mixing and matching the PTR record to various possible
combinations of host names and domain names.
If you see "REVDNS:" or "MISSING_REVERSE_DNS" in replies to E-mails you
send to us, it means that you are missing this reverse DNS entry. You
won't see this in replies to E-mail to this list, though, since we just
check the "first hop" (the IMail server).
-Scott
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