Spampd is a program used within an e-mail delivery system to scan messages for
possible Unsolicited Commercial E-mail (UCE, aka spam) content. It uses
SpamAssassin (SA) to do the actual message scanning. Spampd acts as a
transparent SMTP/LMTP proxy between two mail servers, and during the
transaction it passes the mail through SA. If SA decides the mail could be
spam, then spampd will ask SA to add some headers and a report to the message
indicating it's spam and why.