S/MIME Verification

March 2026How to verify the S/MIME signature of an email

S/MIME Signature Verification Screenshot — The S/MIME signature-verification guide.

All my work-related emails are digitally signed with S/MIME (see the imprint). Digital signatures can be used by recipients to confirm that a message really came from me and was not tampered with by other parties. Unfortunately, digital signatures are only useful if the recipient knows what to look for and how to verify the validity of the signature.

For this reason, I built (actually: vibe coded) a brief online guide that explains how to verify a digitally signed email, with client-specific step-by-step instructions for common email apps (Outlook, Thunderbird, Gmail, and Apple Mail). My signed emails always contain a link to this info page.