User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.5) Gecko/20041107 Firefox/1.0 Build Identifier: Thunderbird/0.9 Thunderbird should support per-recipient rules for signing and/or encrypting messages with S/MIME. This could be implemented as a rule dialog, similarly to what has been done with enigmail, or preferably as an option in the address book. Reproducible: Always Steps to Reproduce: 1. 2. 3.

See Suite bug 154334.

I concur, this is a necessary feature to make S/MIME useable. The referenced bug 154334 is similar but not a duplicate. There needs to be a way to sign all mail except that mail sent to certan domains that don't support S/MIME (AOL, Hotmail, WebTV, etc), and to certain individual users who don't know how to upgrade their outdated email clients. The users of these clients/services tend to be easily confused by strange attachments, which is exactly how S/MIME signatures appear to them. The enhancement as described in the original post would solve this problem beautifully, and allow users to successfully use S/MIME signatures and encryption on most of their email, without unnecessarily confusing Grandma any more than she already is.

Enigmail's solution is fairly mature. That would be ideal IMO.

imho a valid request. Confirming.

FYI, there's an add-on available which sets encryption/sign options based on address book fields: https://addons.mozilla.org/thunderbird/addon/security-settings-from-addr/