Hi @Penny Miller ,
What's the version of your Outlook 2019 (File>Office account>About Outlook), please first ensure that you have updated to the latest version of Outlook client. Consideirng the issue only occurred on this specific user, have you checked if there are any differences between this client with others(such as client version or install any programs or add-ins)
In order to further confirm if the issue is related to your client, it's suggested to log in to your owa and create the draft to test if the issue could be reproduced there.
If the issue occurred on your client only, based on my research, some add-ins in Outlook may cause it, it's suggested to restart your Outlook in safe mode to check(Windows + R > type "Outlook.exe /safe">enter)
If it could work normally in safe mode, please try to disable your COM add-ins gradually to check which causes it(File>Options>Add-ins>COM-add-ins>Go>uncheck the option)
If your issue has any update, please feel free to post back :)
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