Merged upstream (KF 6.28)

Notes: This currently relies on CryptoHelper::decryptMessage() in mimetreeparser. That in turn re-implements all the decrypt handling that we already have elsewhere, except it fails on a lot of the (many) corner cases. In Outlook, it already breaks at the message no longer being properly typed as multipart/encrypted.

https://invent.kde.org/pim/mimetreeparser/-/merge_requests/103

Some words of explanation:
GpgOL, in some cases, will encapsulate the true MIME representation of an outgoing multipart/encrypted or multipart/signed messsage into an application/octet-stream part, which is technically inserted as an attachment with filename GpgOL_MIME_structure.mime. This is probably done to work around mangling of the MIME tree by Outlook/Exchange.

The missing signature was a problem on my end. The customer mail (to ted / exchange server) works fine if the cert is in the keyring. The testmails (via outlook imap) are fine, too. I still need a better test setup for mails to our exchange accounts, but this is enough to rule out a problem in gpgol. I adjust my former message accordingly.

Hmm ich sehe weiterhin die Signatur.

The missing signature indication can also be seen now in the customer mails sent via kmail (ted:INBOX, e.g. 18.02. 12:52). This was fine before.

The basic fix for the msg box looks good to me on gpg4win-5.0.2-beta2 @ win11.
There's only no signature shown anymore, not even for the formerly working case 1.
Note: I also tested those mails sent to an exchange server with the same result as via IMAP.

Note for mails with 2 attachments, where the warning is displayed: Those mails can't be moved in Outlook/GpgOL

Regarding 8. encrypted/signed vcard attachment:

Notes:

• "Save encrypted" is only "Save" in the UI.
• This is still reproducible in gpg4win-5.0.0-beta476 @ win11

I can't reproduce your problems. Can you get me the exact test files you used?

Resolved without further testing, all further improvements in new tickets

Tested on gpg4win-5.0.0-beta413 @ win11.

(removed unfinished text)

Done with https://invent.kde.org/pim/mimetreeparser/-/commit/0624268ae545ced59177ce15f92be119ba43025a

Concluded after talking with Carl that there is no need to backport this any more. Therefore retagging this for gpd5x

This should now work on master, I will write here once this is in the next beta