Module Extensions

https://learn.microsoft.com/en-us/office/dev/add-ins/outlook/extension-module-outlook-add-ins

Those are full page plugins, Mailbox and context is not supported, the graph api is supported,

[Registering Mailbox and Item events is not available with this extension point.](Registering Mailbox and Item events is not available with this extension point.)

That means no emails can be opened in new window