Is DNS MX Record Required For Email?

[Krusty]

"Mark Andrews" <Mark_Andrews at isc.org> wrote in message 
news:dsrand$2sl9$1 at sf1.isc.org...
>
>> 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.
>
> Well to send email to a IP address the correct syntax is
> "user@[1.2.3.4]".

Good info. I didn't know that. Thanks.