Mailpile can encrypt your e-mail, search engine and settings.
This protects your privacy, even if your computer gets lost or stolen.
Encryption makes it harder to migrate your data to another e-mail client, slows things down and may increase the odds of data loss.
Losing your encryption key becomes equivalent to losing all your mail.
Also keep in mind that the security of your data depends entirely on the strength of your password.
You can change your Mailpile password here.