Need some direction here. I've got a domain called sofmail.com that we use for our Small Business Server 2003. I've got a user who gets a "550 Invalid domain sofmail.com" error when sending to several external accounts.
The message implies that sofmail.com either isn't a real domain, or can't accept E-mail. However, http://www.dnsstuff.com/tools/traversal.ch?name=sofmail.com&type=MX shows that no matter which DNS servers are used, the domain does indeed exist and has an MX record. There doesn't seem to be any justification for the error message you received.
My concern is that the DNS host (MCI) didn't setup the reverse DNS correctly.
That shouldn't be the problem -- if there was a problem with the reverse DNS entry, you should be seeing a different error message (such as "550 IP 192.0.2.25 doesn't resolve"), that refers to the IP rather than the domain.
Being that I'm not a DNS guru I was hoping perhaps someone could shed some light on what's pointing where. I'm thinking that the recipient's mail server is doing a reverse lookup for sofmail.com and can't find it. I think MCI created a PTR for mail.sofmail.com. What should it be?
For reverse DNS (which I don't think is the problem here), the IP address that the outgoing mail is sent from is the one that needs to have a reverse DNS entry. If the E-mail is sent from an IP 192.0.2.25, then 192.0.2.25 is the one that needs the reverse DNS entry (even if there are other IPs that the mailserver uses). http://www.DNSstuff.com has a Reverse DNS Lookup tool that helps point out reverse DNS problems.
-Scott
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