| Program || Classification || Description |
fetchmail transfers email from remote POP and IMAP servers to your local SMTP server. You will need
fetchmail if, for example, you need to retrieve remote email, but can't use your machine as an email exchanger.
| MTA and MDA|
sendmail, which delivers most of the Internet's mail, operates as both an MTA and a MDA. It sends email to and receives email from Internet hosts, and it delivers mail to domain mail handlers.
procmail is a powerful MDA that provides extremely sophisticated support for delivering mail. It allows email to be filtered and tagged before delivery, optionally filing mail into content-specific mail folders.