Enigmail works under Microsoft Windows, Unix-like, and Mac OS X operating systems.

Enigmail can operate with other mail clients compatible with PGP/MIME and inline PGP such as: Microsoft Outlook with Gpg4win package installed, Gnome Evolution, KMail, Claws Mail, Gnus, Mutt.

Enigmail adds an alternative mechanism where cooperating users can instead use keys provided by a web of trust, which relies on multiple users to endorse the authenticity of the sender's and recipient's credentials.

[5] Enigmail has announced its support for the new "pretty Easy privacy" (p≡p) encryption scheme in a joint Thunderbird extension to be released in December 2015.

[9] The background is a change in the code base of Thunderbird, removing support for legacy add-ons.