User-Agent: Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.9.1.1) Gecko/20090715 Thunderbird/3.0b3 Currently in the S/MIME preferences there are only to options for encryption: - always - never A further option should be added for - automatically encrypt if Certficate is available (currently there's only a workaround by using the Addon "Auto Enryption" https://addons.mozilla.org/de/thunderbird/addon/5780 , but I would prefer having this method built into TB as a standard option.) Having only the options "always" and "never" you are always forced to select/unselect encryption within the compose window manually, depending on whether you are in possession of the recipient's cert or not - what you always will have to check in advance. Otherwise you might get a "error message" in case of using "encrypt always" if you don't have the recipient's cert available. Respectively you might forget to encrypt a secret mail before sending if you have chosen "never encrypt" although you've got the recipients cert available. ADDITONALLY even when the option "Automatically encrypt if Certficate exists" is available one day and activated, within the compose window it should be possible to disable encryption manually via the lock icon afterwards for this mail (maybe this would be a standard option anyway then). Reproducible: Always

This looks like bug 442180, don't you agree ?

Rosa ^^^ ?

You are right, it's a duplicate of bug 135636, which I didn't find before. Sorry.