List of mail server software

All such figures are necessarily estimates because data about mail server share is difficult to obtain; there are few reliable primary sources—and no agreed methodologies for its collection.

Surveys probing Internet-exposed systems typically attempt to identify systems via their banner, or other identifying features;[1] and report Postfix and exim as overwhelming leaders in March 2021, with greater than 92% share between them.[1] While such methods are effective at identifying mail server share for receiving systems, most large-scale sending environments are not listening for traffic on the public internet and will not be counted using such methodologies.

• Mail-in-a-Box
• iRedmail[4]
• Modoboa[5]
• Mailcow[6]
• Poste.io[7]
• docker-mailserver[8]
• Mailu[9]

• Comparison of mail servers
• Message transfer agent