What is HELO?

[michigan]

Hi Cisco gurus.

I've recently been asked to trouble shoot a particular email issue at work. I can't seem to find a straight out answer as to what the heck "HELO" is, what it stands for or why DNS entries rely on this so much?

Can someone please give me the HELO 101 in a sentence or two? I appreciate your time. Thanks.

 

[writemem]

I'm not sure if this will help but i remember that you can telnet to your mailserver on port 25 (smtp) and it will connect. You can issue a HELO command and it will let you specify user to send to your reply address. That's about all i can remember it does have to do with smtp though. at least what i remember. Sorry i couldn't be more helpful.

Mark

 

[yizhar]

HI.

"HELO" is one of the commands of the SMTP protocol, and is used by the sender client or server to identify itself (the sending machine or software) to the receiving SMTP server.

For more details, read the SMTP RFC.

In many cases the HELO command is followed by the sender computer name.

Some SMTP servers do not care about the HELO argument, but some servers might use it for relay decisions, and might use DNS to check if that the originating sender ip address matches the FQDN specified in the HELO command.

Bye
Yizhar Hurwitz

http://come.to/yizhar

http://teachers.sivan.co.il/yizhar