Not compatible with Sonoma Mail digital signature and encryption feature, which I use with the apporpriate certificates.
Expected:

Actual:

When viewing signed emails, the Signed label isn't displayed with the MailTrackerBlocker message security extension. Also the signing/encryption icons are greyed out in the message composer. Tested with Actalis' free S/MIME cert.
Content-Type: multipart/signed;
boundary="Apple-Mail=_CB35ED7D-E91E-4556-85DF-1AFDCCA86A12";
protocol="application/pkcs7-signature";
micalg=sha-256
Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3774.600.62\))
Subject: signed test
--Apple-Mail=_CB35ED7D-E91E-4556-85DF-1AFDCCA86A12
Content-Disposition: attachment;
filename=smime.p7s
Content-Type: application/pkcs7-signature;
name=smime.p7s
Content-Transfer-Encoding: base64
Expected:

Actual:

When viewing signed emails, the
Signedlabel isn't displayed with the MailTrackerBlocker message security extension. Also the signing/encryption icons are greyed out in the message composer. Tested with Actalis' free S/MIME cert.