Honestly, shouldn't we rescue literally everything here? Otherwise we risk inadvertently introducing an error into someones app that they didn't intend.

Of course, that person would have to (1) choose to send notifications synchronously; while (2) knowing they're working in error prone code; with (3) a poorly configured, untested or unreliable mail setup. Given 1-3, I don't know how much we should try to help them.