- related to Email
It is available at (Hutzler et al. 2007). I read it for a high-level sense on what is MUA, MSA, MTA and MDA.
My understanding after reading it:
- MUA is the interface the actual user (human being) uses, and it submit emails to MSA, or receive email from MDA into (MUA's) mailbox.
- MSA accept the submission and do some processing on it (or reject it), and relays this email to an MTA.
- MTA relays the message in a potentially long chains of MTAs, eventually the email reach the MDA it clarified as the destination.
- MDA accepts the email or reject it, and deliver it to the MUA.
+-------+ +-------+ +-------+ +-------+
| userA |-------->| MUA |-------->| MSA |---->| MTA |
+-------+ +-------+ +-------+ +-------+
|
|
v
+-------+ +-------+ +-------+ +-------+
| userB |<--------| MUA |<--------| MDA |<----| MTA |
+-------+ +-------+ +-------+ +-------+
Reference
Hutzler, Carl, Dave Crocker, Peter Resnick, Eric Allman, and Tony Finch. 2007. “Rfc5068 Email Submission Operations: Access and Accountability Requirements.” Internet Engineering Task Force. November 2007. https://datatracker.ietf.org/doc/html/rfc5068.