>4. The problem is Imail SMTP says HELO client1domain.com to the destination
>SMTP. Some SMTP servers perform reverse lookup for host names, and if a
>retrieved host name and HELO's one doesn't match, mail is rejected.
I have never, ever seen a mailserver do this (although I believe Len
has). Mailservers that reject the mail based on the HELO not matching the
reverse DNS entry are violating the RFCs, and will drop HUGE amounts of
legitimate mail.
Note that AOL will often silently drop E-mail from mailservers with no
reverse DNS entries (it has some sort of weighting system), which is VERY
strict, but there is no sign that even they care about the HELO/revdns
matching.
>So if his SMTP says HELO client1domain.com, a PTR record for the name
>client1domain.com has to exist in Reverse Lookup Zone
>333.222.111.in-addr.arpa, period.
No. There's no need to give in to those people. There's no reason to have
a reverse DNS entry of mail.example.com if the mailserver says HELO
mail.other_domain.com (except to please the very, very small percent of
mailservers that do that, knowing they will not get a lot of their
legitimate mail).
>5. The trick is you may have only one PTR record for some particular IP
>address, and I assume he has it already for imail.earthlink net (to
>simplify, we are not talking about round robin stuff... never tried round
>robins in reverse zones, though)
A lot of people have multiple PTR records, but virtually all reverse DNS
tools only look at the first entry, so having just one reverse DNS entry is
the best practice.
-Scott
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