c9dev / penguin-mail

Mail and calendar for Linux and macOS. Gmail and IMAP accounts, Google Calendar, contacts, OpenPGP and S/MIME. GTK4 and libadwaita, written in Rust.

jstedfast / MailKit

A cross-platform .NET library for IMAP, POP3, and SMTP.

jstedfast / MimeKit

A .NET MIME creation and parser library with support for S/MIME, PGP, DKIM, TNEF and Unix mbox spools.

bbottema / simple-java-mail

Simple API, Complex Emails (Jakarta Mail smtp wrapper)