S/MIME

S/MIME (Secure/Multipurpose Internet Mail Extensions) is a standard for signing and encrypting e-mails end-to-end. Usually signing, verifying and encrypting/decrypting is done by the mail client.

Using S/MIME with your standalone email client such as Thunderbird, Outlook or Apple Mail is supported.

S/MIME Support in Webmail

SpeedZone Webmail can verify the validity of incoming S/MIME signatures and display the signature status to the user.

Signature validity is verified against the same root certificates as used in Thunderbird.

Important!

SpeedZone Webmail cannot:
• sign emails
• encrypt emails
• decrypt encrypted emails.

S/MIME signing and encryption must be done in a separate email client, such as Thunderbird or Outlook.

Updated on 18. May 2026
Was this article helpful?

Related Articles