Unable to Decrypt with PGP Desktop - Email messages and attachments are converted to winmail.dat files
Article ID: 155940
Updated On:
Products
Issue/Introduction
When sending messages to users who do not use Outlook (including Web Messenger users), messages and/or their attachments may come through as MS-TNEF encoded winmail.dat files.
Cause
This will occur because the message uses the Outlook-proprietary Rich Text Format. This format is only compatible with Microsoft Outlook email clients.
Resolution
Important Note on Outlook and Exchange Support: PGP Encryption Desktop supports Outlook with standard email protocols, such as MAPI, POP, IMAP and SMTP.
Exchange 365, Exchange Online, Outlook 365, Office 365, Microsoft 365, or any other similar variants by Microsoft, are fully supported.
PGP Encryption Desktop uses these standard protocols that comply with specific standards and as long as the standards do not deviate from the above, Email Encryption will work.
Even MAPI using HTTPS/RPC is supported and works just fine. For more information on this, reach out to Symantec Encryption Support.
IMSFR-512/EPG-22854
This issue is not caused by any setting on the PGP Server or within PGP Desktop, but the TNEF encoding being used on the Exchange server level.
The following knowledge base article from Microsoft details how to verify your Outlook and Exchange configuration to prevent this from happening:
How to Prevent the Winmail.dat File from Being Sent to Internet Users
How to Configure Message Format Settings for a Remote Domain​
Additional Information
IMSFR-1022
155681 - How to use Email Encryption with PGP Desktop and Outlook (Symantec Encryption Desktop)
163281 - PGP Server cannot decrypt an attachment attached to a Rich Text Format message (Symantec Encryption Management Server)
155940 - Unable to Decrypt with PGP Desktop - Email messages and attachments are converted to winmail.dat files
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