In this post, we’re going to dive into IMAP. IMAP stands for Internet Message Access Protocol, and it’s the open standard that describes how to access messages in an email mailbox. While IMAP is an important part of receiving emails, it’s not always the easiest thing to implement (or understand). In short, IMAP is the protocol that email clients like Mail.app, Thunderbird, and Mailspring use to download messages from your email account and to make changes like archiving messages or sorting them into folders.
A Brief History of IMAP
IMAP was originally created by Mark Crispin at Stanford in the 1980s. Crispin later moved to the University of Washington and spent 20 years there working on the IMAP specs and reference implementation. The IMAP specification comes in the form of a “Request for Comments," or RFC, which is basically a memo describing how to implement the protocol that has been adopted as a standard by the Internet Engineering Task Force. RFCs may be revised to make clarifications or changes, and the current RFC that describes IMAP is RFC3501 which was published in 2003. That’s right: the protocol most mail clients use to sync email is over 15 years old!