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 DomainName.com" 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 "1.2.3.4", which is of course not my IP. But it's easier to type.) There 
is no DNS entry for "1.2.3.4" anywhere.

"http://1.2.3.4" gets into my web server without a problem.
"ftp 1.3.3.4" (DOS prompt) gets to my FTP folder without a problem.

But..., when I send an email to "User at 1.2.3.4" it fails. I have a mail 
account with a Windows based ISP and am experimenting sending mail from it 
to "User at 1.2.3.4". 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 1.2.3.4" 
account.

Any thoughts/tips greatly appreciated. 



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