"FAQ": Frequently Answered Question -- something that comes up a lot on
USENET and mailing lists, annoying the "regulars."  Also refers to a document
containing a collection of these frequently asked questions and their
answers.  This document is therefore a FAQ.

"MLM": Mailing-List Manager -- the software handling the subscription list
and (usually) distribution of mail.  In contrast, the person who owns or
moderates a list is usually called the list owner (though this is debated).

"MTA": Mail Transport Agent -- the program handling actual delivery of mail.
On Unix systems this is usually Sendmail, Smail, or Zmailer.  On IBM
mainframes running VM (I don't know about other IBM OS's), you may see LMAIL,
XMAILER, or IBM's SMTP product; on VMS systems you may see PMDF or MX.

"MUA": Mail User Agent -- the program the user interacts with to read and
write e-mail.  On Unix systems, popular MUA's are Elm, Pine, mail, mailx,
mush, etc.  On PC's, some common MUA's are cc:Mail, Pegasus (PMAIL),
Microsoft Mail, etc.  On IBM mainframes, you see mostly Rice Mail (MailBook)
under VM, and others like PROFS under the other OS's.  On VMS systems, common
MUA's are VMS Mail and All in 1.