Hi Jason,
In this situation, please try the following two ways to send Excel or Word attachment and see if there is any difference.
1.
Send Excel or Word attachment in Outlook via Click Insert > Attach File.
2.
Send Excel or Word attachment in Excel or Word via Click File > Share.
In addition, it is suggested to
repair your Office installation.
Please try my suggestions and let me know the result.
Regards,
Aidan Wang
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