Is DNS MX Record Required For Email?

Scooby Scooby at Scooby.doo
Sun Feb 12 23:22:31 UTC 2006

Is it possible to by-pass the DNS lookup for email like it is for HTTP and 
FTP? Is there something about the MX record in DNS that requires a 
"User at" type address for it to work?

Here's why I ask.

I have a static, always-on IP address coming into my house. I run Web and 
FTP servers on my PC.  They work fine, and have for a long time. My OS is 
Windows NT 2000 Professional.

When I scan my ports from a remote machine I get what I expect, which is:
21 (FTP): Open
25 (SMTP): Open
80 (WWW): Open
110 (POP3): Open
143 (IMAP): Open

I only share data with people I do business with. I prefer to just use my IP 
address instead of aliasing it with a domain name. (For these examples I'll 
use "", which is of course not my IP. But it's easier to type.) There 
is no DNS entry for "" anywhere.

"" gets into my web server without a problem.
"ftp" (DOS prompt) gets to my FTP folder without a problem.

But..., when I send an email to "User at" it fails. I have a mail 
account with a Windows based ISP and am experimenting sending mail from it 
to "User at". It doesn't work.

I have my the mail server on my machine configured correctly. And have the 
domain/accounts set up like they should be, including a "User at" 

Any thoughts/tips greatly appreciated. 

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