Unable to decrypt with PGP Viewer
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Unable to decrypt with PGP Viewer


Article ID: 174159


Updated On:


Desktop Email Encryption File Share Encryption Drive Encryption


PGP Viewer allows users who do not have Email Messaging enabled to decrypt PGP encrypted messages.

After opening PGP Viewer, the user drags and drops the encrypted message from the Outlook Inbox to the PGP Viewer window.  You can even drag and drop .pgp files from the machine to PGP Viewer to decrypt.

However, this functionality does not work with 64-bit Outlook or with Microsoft Office Professional Plus 2013 and above using Click-to-Run.

An error message similar to the following is displayed where the Subject of the message is Test:

PGP Viewer was unable to open "Test.msg".

Error: Not a mail message


  • Desktop Email Encryption prior to release 10.5.1.
  • Microsoft Office Professional Plus 2013 and above using Click-to-Run.


PGP Viewer uses the Microsoft IConverterSession API. This API is not available in Microsoft Office Professional Plus 2013 and above using Click-to-Run.

To determine whether Outlook is using Click-to-Run, please refer to this article. For example, if this registry key has a REG_SZ value of en-us then you are running Outlook Click-to-Run:



Upgrade to release 10.5.1 or above.

Starting with release 10.5.1, PGP Viewer is compatible with 64-bit versions of Outlook and with Click-to-Run versions of Microsoft Office Professional Plus 2013 or later.

If you cannot upgrade, please use one of the workarounds below to decrypt messages using PGP Viewer:

Workaround 1: If the encrypted message has an attachment named Message.pgp it is a PGP/MIME encoded message. Drag and drop just the Message.pgp attachment to PGP Viewer in order to decrypt it.

Workaround 2: If dragging and dropping the Message.pgp file does not work, save the Message.pgp file to your computer and from there, drag and drop it to PGP Viewer to view the message. 

Workaround 3: If the body of the encrypted message begins and ends with the following text then it is encrypted with PGP Partitioned encoding:



To decrypt a PGP Partitioned message:

  1. Select all the text in the body of the message and copy it to the clipboard.
  2. Create a new text file using Notepad.
  3. Paste the text from the clipboard into the new text file.
  4. Save the text file.
  5. Drag and drop the text file to the PGP Viewer window.

Additional Information