I'm trying out Purely Mail. Unlimited email addresses across unlimited custom domains.

I have a cool setup where I have setup an email account at service@service.mydomain.tld, but it's setup as a catchall for *@service.mydomain.tld (and allows gmail-style tagging). This means I can fill out service forms by inventing addresses on the fly like LemonadeStand+Signup@service.mydomain.tld and the email shows up in one unified inbox, the subject line will include [LemonadeStand], and the message will have the flag 'Signup'.