If you are facing the below error with your MDaemon Antivirus with the attachments, you can try the following solution .
ERROR:
Below is the error and the solutions.
X-MDBadQueue-Reason: ClamAV detected a password-protected/encrypted file
(Heuristics.Encrypted.PDF)
******************************* WARNING *******************************
The message has been scanned by SecurityPlus for MDaemon and was found
to contain an attachment that could not be scanned. Information on the
attachment and action taken is provided below.
******************************* WARNING *******************************
SOLUTION:
If you are running MDaemon version 17.5 or below, MDaemon have a separate ClamAV plugin option in the Security Menu. In the ClamAV plugin menu is where configurations can be made for processing messages that cannot be scanned.
Updated versions of MDaemon have a single exclusion file in the Security > Antivirus > Antivirus Scanning menu.
Check Configure Exclusions next to the "Quarantine messages that cannot be scanned" check box.
You can even allow password-protected files to be exclude from the scanning by checking the box of “Allow password-protected files in exclusion list..”
And click OK to save changes.