Microsoft SQL - Microsoft SQL is a best in class relational database management software that facilitates the database server to provide you a primary function to store and retrieve data.
Cryoserver - Cryoserver is an all-in-one email archiving solution that empowers you to preserve your email in a tamper-evident archive, making you transform your data into a useful archive for everyday use.
MySQL - The world's most popular open source database
Gmvault - Backup the emails in your Gmail account.
PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
imapsync - Console-based utility for migrating IMAP mailboxes.