Electronic mail, commonly called email or e-mail, is a method of exchanging digital messages from a sender to one or more recipients.
Modern email operates across the Internet or other computer networks. Some early email systems required that the sender and the recipient both be online at the same time - a system currently known as Instant messaging. Today's email systems are based on a store-and-forward model. Email servers accept, forward, deliver and store messages. Neither the users nor their computers are required to be online simultaneously; they need connect only briefly, typically to an email server, for as long as it takes to send or receive messages.
Email architecture is rich and varied; you should probably indicate whether your question concerns email-address manipulation, email composition (rfc822, mime, email-headers, html-email, etc.), message submission and transport (smtp, x400), or a particular mailbox storage and access protocol (pop3, imap) or perhaps a particular email-client. There is a large number of additional tags you can use.
Programmers coming from modern protocols such as JSON and HTTP will be surprised to learn about the many layers of standards that they have to work with in order to be able to use 8-bit data, multimedia, Unicode, internationalization, tagged content, etc. The MIME standards in particular should be at least vaguely familiar.
- Email (Wikipedia)
The tag email can be used for any programming related problem in implementing features of emailing messages from one client to another. Ask about specific email server related problems at Server Fault, another Stack Exchange website.
Common problems which are not programming-related include
- Port 25 is blocked and you get
- Relay access denied
- How to send emails and avoid having them being classified as spam
- Off-topic: "My email isn't spam" on meta.stackoverflow.com
mime pop3 smtp imap mailto etc