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Sophos Central E-Mail - S/MIME signed emails are getting invalid

Peter Riederer

Hey Folks,

we are evaluating Sophos Central E-Mail and experiencing issues with incoming S/MIME signed e-Mails. The Signature is getting invalid, and our security appliance cannot validate the signature/certificate anymore. E-Mails not routet via E-Mail Central from same sender, dont have any issues.

We already created an exception in data control (forward incoming signed e-mails to new gateway) which always applies successfully, but there is still something happening or getting changed on the email.

Are there any issues known with signed e-mails? Or what else can we do?

Thx a lot in advance.

Regards

Peter



Edited tags
[edited by: Raphael Alganes at 2:28 AM (GMT -7) on 30 Jun 2023]
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  • 0

    Same problem at our end with enabled Smart Banners and Time-of-Click Protection. Will probably always be the case as soon as Sophos changes anything in the content of the email. It could be possible that the last mile to the email client has to be re-signed. Just like the firewall does with SSL connections.

  • 0 in reply to LuNie

    Time-Of-Click Protection is a good point, as well. Didnt thought about that.

    nevertheless, i dont get it why there are some emails which are valid and neither smartbanners and TOC-Protection are applied, and others not. Sophos just needs to apply a rule in the backend, that signed emails will never get touched and stay unchanged. i dont want to create an exception again for senders which send signed emails.

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  • 0 in reply to LuNie

    Time-Of-Click Protection is a good point, as well. Didnt thought about that.

    nevertheless, i dont get it why there are some emails which are valid and neither smartbanners and TOC-Protection are applied, and others not. Sophos just needs to apply a rule in the backend, that signed emails will never get touched and stay unchanged. i dont want to create an exception again for senders which send signed emails.

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