Hi RyanD1989,
>> but whenever the emails send through Outlook from the app, they come out formatted as plain text.
Could you please provide more details about how these mails are sent through Outlook?
Does this issue appear when you attempt to send mails to particular recipients?
To help narrow down the issue, please try directly composing and sending the email in Outlook client and see if the promblem persists?
Besides, as we have little information about the third party app you mention above, it is also encouraged to contact the custom support of the third party app to see if there are other people encountering the similar issue.
Please feel free to post back with any findings.
Best regards,
Yuki Sun
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