In the default setup of the program, the user is given a public and a private PGP key, for the purpose of (respectively) receiving encrypted email and then decrypting it.

The client takes an opportunistic approach to finding other users to encrypt to, those that support it, and integrates this in the process of sending email.

[9][10] In the middle of the campaign, PayPal froze a large portion of the raised funds, and subsequently released them after Mailpile took the issue to the public on blogs and social media platforms including Twitter.

[11][12] The first publicly tagged release 0.1.0[13] from January 2014 included an original typeface (also by the name of "Mailpile"), UI feedback of encryption and signatures, custom search engine, integrated spam-filtering support, and localization to around 30 languages.

[14] July 2014 This release introduced storing logs encrypted, partial native IMAP support, and the spam filtering engine gained more ways to auto-classify e-mail.