Mail programs with S/MIME support (MS Outlook and others)

13. April 2023

What is S/MIME support?

If a mail program supports S/MIME, then it can check GLOBALTRUST/A-CERT ADVANCED signed mails for the integrity of the content (intact/authenticity of the content).

Depending on the certificate management used, the authenticity of the signer (authenticity of the sender) can also be confirmed immediately, or the user must also download the GLOBALTRUST root certificate from our website:

SHA1 Fingerprint=34:2C:D9:D3:06:2D:A4:8C:34:69:65:29:7F:08:1E:BC:2E:F6:8F:DC

We therefore recommend always sending a reference (link) to the root certificate and its fingerprint with signed emails. This means that the recipient always has the opportunity to update his certificate master administration and to check the authenticity of the mail content and the mail sender.

Which mail programs offer S/MIME support?

In addition to Microsoft Office Outlook, Windows Mail, Apple Mail and Mozilla Thunderbird, there are a number of other programs that support S/MIME.

Can signed mails also be read by other mail programs?

In the case of mail programs that do not support S/MIME, the signature and certificate are interpreted as other attachments. The sender’s certificate can be determined, but not the integrity of the mail content.

Can webmailers evaluate signatures?

Most webmailers, such as Hotmail, Gmail, … cannot evaluate the signatures of signed emails. In these cases, the certificate for the signature is displayed as an attachment and the mail is treated and displayed like an unsigned mail.

There is a plugin for the frequently used open-source webmail solution “SquirrelMail” with which the S/MIME data of received e-mails can be checked. However, you cannot use it to send signed e-mails.

There is a plugin for the Firefox browser that you can use to send signed e-mails via the Gmail web interface.

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