From iA wiki
Acronym: Mail User Agent
Software that make you able to read and write mails and, in most cases, send them to someone else too ranging from simple to highly complex. Clients come in every flavor so it is usually the user's personal choice which one to use.
A list of clients
This list is not exhaustive
- Eudora (Mac, OS X, and Windows)
- Mozilla Mail/News - Mozilla's email and news client
- Pegasus - (DOS, Windows)