Opening a P7S file: How to proceed

If you want to open a P7S file, you need a specific email program. This is because it uses a secure email communication method.

Opening a P7S file: How to do it

If you receive an email with a P7S file attached, it is not a traditional file with visible content, but a so-called digital signature. A P7S file is used by email programs to verify and confirm the authenticity of the email or the sender.

• SMIME.p7s is a digital signature that is sent as an attachment by email senders who have set up an email signature certificate on their computer. S/MIME is an abbreviation for Secure/Multipurpose Internet Mail Extension and is an encryption standard that is used, among other things, to ensure the authenticity of the sender of the email.

• To open a P7S file, you need Microsoft Outlook. Right-click on the file and select “Open with,” which will bring up another tab.

• If Outlook is already listed here, click on it. Otherwise, click on “Choose another app” at the bottom. If Outlook is not listed here either, scroll down to the bottom and search for the program manually on your PC.

• Alternatively, Thunderbird can also process S/MIME, provided you have a suitable user certificate stored in the settings. The digital signature is checked and displayed using the integrated certificate manager. This provides a suitable alternative to Outlook.

• If you use Apple Mail, S/MIME is processed automatically. The prerequisite is that the corresponding certificates are installed in the keychain. The signature is then displayed directly in the email interface.

• In Windows, the Certificate Manager plays a central role in processing S/MIME data. This is where trusted certificates are stored that can be used to verify digital signatures. If the sender’s certificate is not known, the signature may be marked as “untrusted” even if it is technically correct.

• In order for a signed email to be fully verified and displayed correctly, a suitable certificate must be installed on the recipient’s system. This can either be the sender’s public certificate or a generally recognized certificate from a trusted certification authority.