Maybe the file was encrypted with a version of gpg4win-3.1.5? We had a serious bug there that sometimes files were corrupted. See: T4332

My understanding of this issue and the fix for it is that Outlook with exchange detects that our mails are S/MIME mails. As the attachments are modified by us outlook wants to save the changes on move. This fails because it can't do the crypto. Leading to the error. This also happens when such a mail is closed.

We did not remove the "<>" from the content id. This worked for the first display but when forwarding they got doubled and it broke.

The code had the assumption that a content-id
could only exist on an attachment for HTML mails as it otherwise
does not make sense.

I was able to reproduce this when I forwarded the mail after opening it in a new window. Somehow that appears to influence it.

Closing this as the moving problem was fixed.

I guess you are the only person who does it. But yeah. I agree that it should be fixed.

I agree with @dkg here.

When doing a "gpgsm --with-validation -k foo" (assuming you have a cert foo) gpgsm now goes into a loop and prints the certficates that match "foo" over and over again. I have not tested if it was caused by this change but I think it is likely.

Smartcard support is a big advantage of using the GnuPG backend and it should work of course.

I imported 39 certificate files at once with Kleopatra with about 700 certificates and it worked. Took a long time though so It would be nice if Kleopatra would show a progess indicator or some indication that the import is running. But this is a different issue.

Or a better tl;dr; When you send mails without "inline" option everything is fine and standardized. The problem is that the old version of GpgOL that your college uses is too stupid to handle this ;-)

Yes your colleague should or basically needs to upgrade. 2.2.3 is very outdated. There are security issues that were fixed by then etc.

What client does your colleague use so that you have to use PGP/Inline?

The last lines that the process currently holding wrote in the log:

To reproduce this issue I started Kleopatra with an empty GNUPGHOME and imported 10 S/MIME certs at once (which spawns a gpgsm process each) with enabled logging.

Thanks for the explanation.

As this update lists multiple issues and following fixes for them, maybe it was resolved by Microsoft?