Hi,
So I was testing which kind of message structure would be the best fit for sending out messages with more than one signature part. I tried 3 things:
Message according to 1this(having two signature parts in a 'multipart/mixed' part inside 'multipart/signed' message. My MUA(*mu4e*2) fails to find any signature part at all in this
A 'multipart/alternative' message with each part having same structure and each one having different signature. Now although from rfc20463 it is not a thumb rule to have different 'content-type' for each alternative part in a 'multipart/alternative', but I think MUAs would get confused if they find both alternative parts completely same(in structure). My MUA shows both parts and thus repeats data. Although it shows two signature parts too.
This third type was just my idea, does not follow rfc3156 obviously. I simply added another signature part to the original message and my MUA reads it nicely showing two signatures.
I have attached all 3 type of message, each in a different file. Please can you place it in your maildir and check how your MUAs respond to it and report here? The message signature will not be verified(the signature text is actually gibberish), this experiment is just to check how the MUAs handle the message with such a structure.
-- Abhilash Raj