Outlook

NewNew Outlook: S/MIME signature cannot be verified in secondary account, attachments missing

The new Outlook reports that the S/MIME signature cannot be verified in a secondary account for a shared mailbox and does not display attachments. This article explains the difference between Clear Signing and Opaque Signing, why attachments disappear from opaque-signed messages, why the new Outlook processes S/MIME only in the primary account, and what workarounds are available, including unpacking smime.p7m with PowerShell or OpenSSL.