Dec. 31, 2017
8:24 a.m.
There's a lot of open source SMTP and POP/IMAP servers, pretty good list in this Wikipedia article. Other than Postfix I don't know how many have EAI support.
Exim. Qmail in binary form in some distrbutions, or if build from source, either from my github account or in one of the patchsets that include it. Sendmail if you build from the source on my github account. Four commercial ones that I know of (I have the list at home). POP/IMAP is worse. I have one, fully compliant, but don’t want people do use it (I want to retire that code). None of the majors have EAI support. Arnt