With the upcoming release 1.8, Enigmail will become so easy to use do that I can even recommend it to my non-techie family and my friends. I’m just waiting for the translations to be finished and the final release. It’s a great improvement over all previous releases.
The main thing Enigmail introduces is ease of use. Even if one didn't saw OpenPGP before, he/she will easily learn how to use it to protect email messages.
The "dropdown box" way of enabling/disabling encryption or signing is a bit annoying to use, but aside from that UI annoyance, otherwise, it does the job well. Currently annoyed by a bug that prevents `Bcc:` recipients, but that is hopefully temporary and has supposedly been fixed in the next release.
Enigmail enables Mozilla Thunderbird users to use OpenPGP (using GnuPG). While this should be an integrated part of any email program today, Enigmail strives to give users the best possible user experience an AddOn can do.
Enigmail does what it promises. It simplifies considerably a process which should occupy your brain for some time under normal circumstances. This and its reliability make it a rather good software. But all this ease of use and your success in using encryption, should rather augment your interest in the topic, stimulate your curiosity and encourage you to get a little background-knowledge. Please do not ask, how secure is it? Rather get the information from any GnuPG//OpenPGP-related documentation. If this thing is too simple, you become the risk.
excelent add-on for thunderbird/icedove and must for sending encrypted email