If i sign an email, the signature is shown as invalid in Thunderburd, FairMail or even in Aquamail itself. on Manjaro and latest Android.
I appear to be having this same issue. Signed mail from Thunderbird works fine in both Thunderbird and Aqua Mail, but signed mail from Aqua Mail is invalid in Aqua Mail and Thunderbird.
Hello guys. I was testing my problem and find out some problems inside Thunderbird too (it appeared only, when digitally signed message had special characters (in Polish language for example there is ę€óąśłżźćń).
The reason in case of Thunderbird, and AquaMail was handling messages by my mailserver itself! You may have same problem.
In my case configuration of amavisd-new was changing email message, so after receiving message was detected with invalid signature (and that was correct, because message was changed between me, and receiver). My amavisd-new configuration was:
# force MTA conversion to 7-bit (e.g. before DKIM signing)
smtpd_discard_ehlo_keywords => ['8BITMIME']
Since conversion is made AFTER singing with S/MIME, then error about digital sign is correct.
To fix it in my case i just disabled whole line by commenting it (just put # before line).
Also in Your scenario it may be Postfix itself (it also have option to convert to 7-bit format).
Check this with Your mail server administrators.
