Email signature verification

How to verify my S/MIME signature

If you received an email from me, your mail app should indicate that the message is digitally signed. Use the client-specific steps below to confirm the signature is valid and inspect the certificate details.

Choose your email client

Select the app you use to see what to look for.

  1. Open the message in its own window

    Open the email in its own reading view so the security controls and sender details are fully visible.

    Mock Outlook message window showing the area where the signed icon appears.

  2. Open the signature details and check the sender

    Outlook should report that the message is signed. Review the sender identity in the signature details popup.

    Mock Outlook signature details dialog showing the valid signature state and sender identity.

  1. Click the signature symbol in the top right

    Open the email and click the small S/MIME signature icon next to the message time in the upper-right corner.

    Thunderbird message view showing the S/MIME signature icon in the top right.

  2. Check the full sender name in the popup

    Thunderbird will open a security popup. Verify that the message is signed and that the full sender name is the expected one.

    Thunderbird security popup showing the signed status and the full sender name.

  1. Open the message and expand sender details

    Expand Gmail's message details so the security and sender information are visible beyond the condensed header.

    Mock Gmail message details view showing where the signed status appears.

  2. Check the signer information

    Look for the signed status and verify that the signer information matches the sender you expect.

    Mock Gmail signer information panel showing signature status and sender identity.

  1. Open the email and look at the message header

    Keep the message header visible so the signed-message badge is easy to spot near the sender information.

    Mock Apple Mail message header showing the signed badge area.

  2. Open certificate details and confirm the identity

    After opening the signed badge details, check that the certificate identity matches the sender you expect.

    Mock Apple Mail certificate details view showing the sender identity.

Using another email client?

Look for wording such as digitally signed, signature is valid, or a certificate viewer linked from the message header. If your client exposes certificate details, confirm that the signer identity matches my email address and that the certificate chain is trusted.