Hiver - Manage Customer Support, Sales and Projects right from your Gmail inbox. Collaborate with Shared Labels, Shared Contacts, email notes, email reminders and email templates
Dovecot - Dovecot is an open source IMAP and POP3 email server for Linux/UNIX-like systems, written with...
Nylas Mail - The Nylas Cloud API powers your application with email, calendar & contacts features. Built-in features for better email, calendar, and contact management.
Postfix - Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail.
Clean Email - Clean Email is an online service that empowers you to take control of your mailbox.
Courier IMAP - The Courier IMAP server is a fast, scalable, enterprise IMAP server that uses Maildirs.