Outgoing mail sends via mail.domain.com but not smtp.domain.com

Factual Questions
1

Well that was bizarre.

Messages wouldn’t leave my outbox (Win 7/Outlook 2007).

Error message was “cannot find the e-mail server. Verify the server information in your account properties.”

I’ve been working, but made no changes (I was aware of).

Everything checked out, restarted Outlook and rebooted the machine—but nothing.

Verified everything with Network Solutions (domain host).

The solution:
I changed the outgoing mail server to mail.domain.com. It had been set to smtp.domain.com.

Now it works. None of the other email accounts I manage would work until I changed them too.

But … but … but that shouldn’t have worked. Well, it should have worked but shouldn’t have made a difference, should it?

What happened?

2

Not sure, but Network Solutions has been having some DNS issues this morning that have affected my email as well. Seems to be a denial of service attack. Mine is back running, but they may not have everyone back up.

3

Confirmation that it’s a DDoS attack at Slashdot.

Lot’s of sites have had issues in recent hours. Including, of course …

4

Thanks. Still, I thought the two addresses went to the same server. Maybe NetSol does some internal routing and the hardware that does that was getting hit by the DDOS.

Wait, ignorance check–do mail. and smtp. go to the same basic place?

5

Logically, it makes sense for both to point to the same basic place from a functional point of view, and generally they will. Nothing forces them to be set up that way technically.

And more importantly, there could be numerous complicated explanations how their load is routed and managed that would explain why one would be bogged down and the other not.

6

From a DNS perspective there is no reason why they can’t. They are just names that get resolved to a network address. Now incoming and outgoing mail use different protocols, POP and SMTP respectively in most cases. Now, those requests using those protocols don’t have to be served at the one network address resolved by DNS- likely NS has a server that forwards those requests to another server, for load balancing if for no other reason.

Or what Fuzzy Dunlop said.

7

To expand on what Mike H said, a mail server doesn’t even have to be named. For several years the mail server at the school I work at had no name – you had to connect to it by its IP. (It still had an MX record, of course.)