That means that the GnuPG Backend does not work. I do not think that the office update is the reason, me and others use GpgOL with the most recent versions of Office Pro Plus without issue.
Have you possibly modified you gnupg config files? If there is a bad value in there it would result in such an error.

Well thanks for reporting it ;-)

I am interested in that. I have a yubikey here that I wish to use productively for brainpool-256 signing, bp-512 (just for fun) encrypting and cv25519 authentication. I need to use brainpool signing and encryption subkeys for VS-NfD compliant communication and I want to be more modern then RSA ;-)

Merged into master. Thanks!

Thanks! I would merge your commits but I'll like to talk to werner tomorrow about the always adding "--with-keygrip" I also think its useful but it might have expensive internal side effects that I am not aware of.

I have difficutlty to accept that as an issue in our tracker. Somehow the GUI for Kleopatra appears to be confusing for your "Sender" which apparently is not you, correct? This results in the wrong keys selected for encryption.
With this amount of information I cannot see any path of change for our software.
Could you maybe provide a screenshot how the recipient selection looks for your user in Kleopatra, so that we can discover why it might be confusing or why the recipients key is not selected correctly?

Thanks for the report. I have observed that the Window is sometimes opened in the background so I accept that this is an issue for Kleopatra somehow and we need to look into it. I know that your problem is a bit different but that is related.

An updated build is available here: https://files.gpg4win.org/Beta/gpgol/2.4.6-beta3/

Yes that is fine with me.

thanks for the report. This is definitely a sore spot and we need to look at it again. I did some experiments a while a go trying to fix this issue but so far I was unable to get to stable results so for now this is a known issue.
I'm a bit suprised that the workaround with not having the mail open does not work for you.

Is this about any special version of Symantec? As far as I knew Symantec Endpoint Security Desktop (or whatever they call it nowadays) supports reading PGP/MIME and even sending it if forced.

This again,...
That error always occurs when the Exchange Server is unhappy with the structure of our PGP/MIME Mails. It has nothing to do with S/MIME, that is only because Exchange only knows about S/MIME, so our PGP/MIME Mails also claim to be S/MIME mails.

Display now looks good to me in all cases. We still keep the subject when a reply / forward is done, but that is the same as before. To do this properly I would have to actually do the protected headers sending,.. as then I could automatically flag such a message to be sent with protected headers. But that would be a new feature and I rather work on properly doing BCC sending as the next privacy enhancing feature.

I'll keep this on needs triage because I don't know what the issue could be. I have a yubikey 5 at hand and just tested it with Gpg4win 3.1.11. It works without problems.

note that it *does* sometimes hide the legacy display part, for some messages, including unfortunately-complex -- that's good! -- but maybe this points to some internal inconsistency:

there is no way to handle this correctly with such messages. The PGP Standard says that PGP Messages may have every encoding. This is a reason why we always talk about "you should use PGP/MIME" as this is basically PGP with added handling for content meta information like the text encoding.

This is fixed now.

This is fixed in Gpg4win-3.1.11

Related task: About subkeys is T4028

Prio raised and assigned to werner as he asked for it.

As a note: They can still be saved when doing file->save as from the message list or by using drag & drop.

We currently do not have the resources to work on it as our focus is more on GpgOL.

Thank you for the good report.

Thanks for the report.

Thanks for the report but I cannot reproduce the issue :-/. In multipart alternative mails GpgOL takes the text part if text mode is set in Outlook.