Fastmail supports regex and wildcards off the top of my head, as I have them set up with my own personal domain. My financial accounts for example are in the format of “bank+xxxxx@domain.tld”
Do you know if they’re required to use the +alias format? I’ve been burnt in the past by bad contact forms silently stripping out special characters out of email addresses.
Verified for myself that it does, thanks! Given how popular FM is I don't know why I missed this prior.