One aspect of app-specific passwords is there is a private record of them with the provider, but there isn't usually a customer-facing interface to see what they are after they are generated. So, I have a secure note in Bitwarden where I can record and annotate them in real-time while they are still in the clipboard. This has saved my bacon more than once, as I routinely evaluate software for later customer recommendations.
Proud user of Fastmail. Oh, since they're based in Australia, I've found you need to use a credit card (made for international use) and not a debit card (which will get blocked by the fraud department instantly).