alt Hacker NewsI recently found out there is a limit to the number of masked emails you can have on Fastmail (1000, iirc -- definitely not infinite for practical purposes). Also, I miss the option of being able to create masked emails on all the domains I connected to Fastmail -- you can only use the "main" one.
If you have 1000, it might be better to just set up a custom domain and just use a wildcard alias.