User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-GB; rv:1.9.1.9) Gecko/20100315 Firefox/3.5.9 Build Identifier: 3.0.4 If a user is required to encrypt certain classes of correspondence, but also needs to send regular mail to recipients without certificates, they must remember always to check the "encrypt" box on mail to certain addresses. Or, they can create an identity with "always encrypt" checked, in which case they must remember always to select this identity sending to certain addresses - or uncheck/unselect it on all regular mail. It would be useful to have a preference "always encrypt mail where possible", which would allow a user to compose and reply to mail as normal, knowing that mail to certain correspondants would always be encrypted. (It may be a regulatory requirement on certain businesses to encrypt email) Reproducible: Always The email program "Alpine" has an identity manager which allows pattern matching by email headers. For instance, a reply to joe@hotmail.com might automatically use the identity "personal" while jane@example.com would use the identity "work". If this model of identity management were adopted in Thunderbird, an identity "secure" could automatically be selected while sending to certain recipients, and an error generated if they did not have a valid certificate.

Andrew, Encryption and security in Thunderbird is increased by TrustedBird project: http://www.trustedbird.org Maybe you can find a solution with this project. Based on bug description, I understand that encrypt or not a message depends on correspondant. In this case, what about a check box in the Address Book to request encryption for specific correspondant. If you agree with this proposal, please update this bug and change Component to Address Book.