Hello @TSIC ,
The issue has already been racked to your account and submitted to the engineers for further review. If and when there's an update you'll be notified by the, but at this time there's no ETA on a fix. I'm not sure which agent described it as "something on the backend," but it's something occurring sporadically in some Office 365 / Outlook programs, which is why the engineers are still collecting info and troubleshooting.
In the meantime, if you expect your contacts will be opening the email in the same email programs, the best available workaround would be to include a View as Webpage link in your emails.
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