In August 2006, rights to the source code were acquired by Cyrus Daboo, the original author.

Mulberry's strengths include strict compliance with Internet standards such as IMAP, LDAP, IMSP, ACAP, and iCalendar, a unique GUI for defining Sieve (mail filtering language) scripts and support for IMAP disconnected operation.

[citation needed] As of August 20, 2006, with version 4.0.5, Mulberry was made available at no cost, but remained proprietary.

The most recent version, 4.0.8, was released for Macintosh (as a Universal Binary), Windows, and Linux on February 23, 2007.

However, Cyrus Daboo made Mulberry available as open source on all three platforms on November 21, 2007, under the terms of the Apache License 2.0.