Winmail.dat body empty

Question

I would need your support, with the latest update of Exchnage 2019 (Exchange Server 2019 CU15 Sep25HU-8 settembre 2025-15.2.1748.37); I have a problem sending emails, recipients receive empty body and any attachments in winmail.dat format.

BR

<PII removed>

Answer 1

It seems to be a problem with one of the three mailboxserver nodes, I'm analyzing the server to understand what is different from the others, i will update you asap

Answer 2

Hi Cacciapuoti Angelo,

Thank you for posting your question in the Microsoft Q&A forum. 

Please understand that our forum is a public platform, and we will modify your question to cover your personal information in the description. Please notice to hide these personal or organization information next time you post error or some information to protect personal data. 

Based on your description, I understand that after updating to Exchange Server 2019 CU15 (15.2.1748.37), emails sent to recipients arrive with an empty body and attachments appear as winmail.dat. This typically indicates that messages are being sent using TNEF (Transport Neutral Encapsulation Format) rather than standard MIME/HTML.

Based on Microsoft documentation, this behavior often occurs when:

Microsoft provides guidance here:
How to specify the email message format to prevent Winmail.dat attachments

Although the article references Exchange Online, the same cmdlets available on on-premises Exchange Server so it worth to follow this support article.

Also, check your Outlook message format settings, as they differ between Classic Outlook and New Outlook:

• Ensure Compose messages in HTML or Plain Text, not Rich Text.
• In Classic Outlook: File > Options > Mail > Compose messages in this format.
• In New Outlook: Settings > Mail > Compose and reply.

I hope the suggestions above help! If you have any further questions, please feel free to share.

Please note that this is the it-it forum. We kindly recommend posting your question in Italian so that more community members can assist you. Alternatively, you may also consider posting on the English forum if you prefer to use your native language. We sincerely appreciate your understanding.

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