Initial situation:

Outlook is used as an email client behind a SEPPmail Secure E-Mail Gateway. The configuration instructs the SEPPmail Secure E-Mail Gateway nevertheless to accept emails that cannot be decrypted and to deliver them to the recipient (Reject mails if S/MIME decryption fails deactivated).When attempting to open an encrypted email originating from the Internet in Outlook, the message

“This element cannot be opened. The name of your digital ID cannot be found in the underlying security system.” appears.

 

Cause:

1.SEPPmail does not have a private key to decrypt the message.
 

Individual remedy:

a)If possible, activate the option Reject mails if S/MIME decryption fails.
 

b)Clarify with the sender where they got the recipient's public key. This false key should be deleted by the sender and the addressed recipient should provide the sender with their current key (in the case of S/MIME by means of a signed email).

 

2.Furthermore, this phenomenon was observed when using ScanMail from Trend MicroTM. The delivered emails are then very small (a few kb) instead of the actual size.
For a long time, Trend MicroTM has (had) a bug that leads to signed emails being destroyed (more precisely: The content is deleted). Outlook then reacts with the above-mentioned error message, which is actually wrong because the message no longer exists.
 

Individual remedy:

Check whether corresponding updates are available for ScanMail.