Postfix vs. Sendmail

[Eric R.]

Brian Kelsay wrote:
> Is a "milter" like a mail filter or something?
> 

Milter is a recent addition to sendmail (versions 8.10 and up have it, 
but it wasn’t until 8.11 that it was a “supported” feature). Milter is 
short for “Mail Filter”. The basic premise is that at every stage of the 
SMTP session — the connection, the HELO command, the MAIL command, the 
RCPT command, etc. — there is a callback where arbitrary C code can 
perform checks on the connection as it is going, and returns one of the 
following: “continue”, “reject”, “accept”, and “discard”.

http://www.samag.com/documents/s=7178/sam0206l/0206l.htm

Found the above today,
E