I have a number of contacts who can only decrypt 3DES, when it comes to S/MIME encrypted mails. I'm aware that this is by far not ideal, but better than no encryption at all.
My problem is, that I can't find a way to force Thunderbird to use 3DES for specific mails. Thunderbird itself doesn't seem to have an option, so I've installed the Enigmail plug-in, which states in the FAQ:
Note that you can force usage of a specific symmetric algorithm by using the GnuPG option --cipher-algo, but this is not recommended; this option can easily break things and is intended for debug purposes only.
This sounds good, but the setting does not change a thing for me.
I'm baffled that there's no obvious solution to this.
How can I force Thunderbird to use a specific encryption cipher for S/MIME encrypted mails?