Mail Retrieval Agent
A mail retrieval agent (MRA ), to collect e- mails from a mail server, or more precisely the Mail Delivery Agent ( MDA), and stores them on the local machine. An MRA is in most e -mail programs ( mail user agent - MUA) integrated and assumes there downloading messages - eg via POP3. But there are also other options such as an MRA accesses the mail. This includes the protocol extensions of SMTP ATRN and ETRN.
Uses a MUA IMAP, this usually directly accesses the MDA and it is technically involved no MRA. However, since many clients also create a copy of messages for offline mode locally, and this component is usually referred to as MRA.
Fetchmail is an example of an MRA, which is not a MUA.