It's only anecdotal but for every site that rejects my personal domain they accept a fastmail.com alias just fine.

I degoogled myself from Gmail/Calendar ... five years ago now? Zero issues with Fastmail that might've affected my life in any way.

I can kinda-sorta remember a few outages, but they were night time in my TZ so I found out about them after the fact.

Also I _love_ how they're not doing the Proton route and trying to become an everything-service. They do mail, calendar and contact sync, that's about it. No VPNs or cloud storage or AI offerings.

Most providers from my understanding don't handle aliases well.

I have a catchall *@domain.tld and Fastmail when it receives an email on an alias, responds correctly with the proper alias.

Also when I compose, it let's me write in a custom alias for the From sender.

Other providers and email clients seem to want you to create an identity for each alias which is a huge burden.