Poste.io Alternatives

An open source mailserver suite.

Mailu is a simple yet full-featured mail server as a set of Docker images.

Mail-in-a-Box provides webmail and an IMAP/SMTP server for use with mobile devices and desktop mail software and also includes contacts and calendar synchronization.

Modoboa is a mail hosting and management platform including a modern and simplified Web User Interface.

A fully fledged, free email server solution, an open source project (GPL v2).

Zimbra is trusted by over 500 million users to increase productivity with a complete set of collaboration tools while maintaining total control over security and privacy.

Web-based IMAP email client

Eudora Internet Mail Server is a highly advanced internet mail system that supports the all kind of email systems and clients either it is IMAP, POP3, SMTP and much more.

Self hosted modern mail server

Synovel Collabsuite is the name of a next generation and open source web server for the Linux operating systems that now features the chat and support for the calendars as well.

Low cost, easy to use Email Server software for virtual, on-premise, or hosted deployments for...

MailEnable is a Windows based mail server and email server program that is packed with the state of the features and functions like antivirus and spam filtering system, webmail management system, cardDAV, CalDAV and much more.

hMailServer is a free e-mail server for Microsoft Windows.