How to reproduce:
- Install Gpg4Win package including all modules
- Ensure you have a valid PGP key-pair for your sender email-address in your truststore (remark: Worked with Thunderbird and Enigmail before)
- Open Outlook and ensure 64-Bit Add-In is loaded
- Do not change any settings of the plugin
- Ensure you have another email account added to your Outlook profile as test recipient
- Open a new mail draft
- Add some subject and text to the body
- Add your second email address as recipient
- Switch on signing at the gpol plugin ribb-on entry
- Send the email (you will have to enter your PK password)
- Receive the email in the inbox of the second account
-> Outlook does no mark it as signed
-> In the preview window gpgol marks it as unsecure (purple plugin icon with question mark)
-> The signature is shown as attachement (asc file)
This behaviour does not apply if the mail is also encrypted. Then both signature check and decryption work.
See attached log of the described process.
Seems to have something to do with my private Kopano mailservers MAPI/MIME conversion. I stumbled over this Kopano ticket from 2018/2019: https://forum.kopano.io/topic/1151/pgp-encrypted-mail-with-gpg4win-and-kopano-from-outlook/22
When sending an email directly via my public email provider, the signature is at least recognized by Thunderbird, even if Enigmail reports it as false.
So imho this trouble seems to be caused by Kopano and not by GpgOL. Unfortunately it seems that is has no priority for the Kopano team. :(