Hi @Brendan May
I'm afraid you can't force Outlook add-in to use Edge because just like the doc says:
Which browser is used depends on:
- The computer's operating system.
- Whether the add-in is running in Office on the web, Microsoft 365, or perpetual (also called "non-subscription" or "one-time purchase") Office 2013 or later.
- Within the perpetual versions of Office, whether the add-in is running in the "consumer" or "commercial" (also called "volume-licensed" or "LTSC") variation.
The recommendation from official is like this: We recommend (but don't require) that you continue to support these combinations, at least in a minimal way, by providing users of your add-in a graceful failure message when your add-in is launched in the Internet Explorer webview.
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Regards,
Yu Zhou