UNIX-derived Systems

The majority of times mail software on a UNIX-derived system (such as Linux, xBSD etc) gets the name wrong is when the mail server operating system _itself_ is improperly configured. Due to idiosyncracies in Linux install procedures, Linux machines are often a bit confused as to what their name is. See Linux/xBSD hostname repair for instructions on how to ensure that the machine name is set properly.

In some cases, your mail server will continue to emit a syntactically invalid HELO parameter even if the machine's name is set properly for the operating system. Check the link for your mail server software to force the mail server to use the right names: sendmail, qmail (applies to MultiTech VPN firewalls and many Linux Plesk installations too), and exim

If you have made changes in this section, we suggest that you repeat the helo testing procedures, then go and delist your IP if everything looks right.

If you haven't found anything wrong, go BACK and go to the "It's not my mail server" section.