There were reports from clients that mails with text/plain were displayed as empty when Outlook is set to only display text mails.
I can reproduce this with a very recent Version of KMail which sets headers like:
From: Andre Heinecke <andre@heinecke.or.at> To: berta.boss@demo.gnupg.com Subject: Signed only Date: Wed, 25 Jan 2023 17:10:58 +0100 Message-ID: <2670375.mvXUDI8C0e@teutates> X-KMail-Identity: 2136111546 X-KMail-Transport: 598470833 X-KMail-Fcc: 11 X-KMail-Identity-Name: Andre X-KMail-Transport-Name: heinecke MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart12143193.O9o76ZdvQC"; micalg="pgp-sha384"; protocol="application/pgp-signature" --nextPart12143193.O9o76ZdvQC Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii"; protected-headers="v1" From: Andre Heinecke <andre@heinecke.or.at> To: berta.boss@demo.gnupg.com Subject: Signed only Date: Wed, 25 Jan 2023 17:10:58 +0100 Message-ID: <2670375.mvXUDI8C0e@teutates> MIME-Version: 1.0 daasdasd --nextPart12143193.O9o76ZdvQC Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part. Content-Transfer-Encoding: 7Bit -----BEGIN PGP SIGNATURE-----
As you can see both the text content and the headers are in the text/plain part. My expectation is that GpgOL interprets this as a Header only part and does not collect the text contents from it.
If there would be a text/html part this would then be parsed correctly.