Hi @Tina Balkema ,
In order to better solve this issue, I want to confirm the following points:
What’s your Exchange server version?
Only one user have this issue or all users have?
Will you receive the NDR only if you send an email with an attachment? Have you tried other types of attachment?
According to my research the error information, there are many possible causes of this issue, please try to following the steps:
- Please try to login to OWA and send a test email with an attachment. then check if it can be sent successfully.
- Please try to run “outlook /safe” in the Run to start outlook as safe mode, To avoid interference from third-party Add-ins.
- Please try to re-create a outlook profile.
- Please upgrade outlook to the last version.
In addition, except for NDR, are there any errors when adding attachments and sending emails?
If possible, please share the complete NDR information with us, we could know more information. But please pay attention to covering the personal information.
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