It would be great if user could provide their own dictionaries, let's say for example colors.txt and fruits.txt.
Then customize alias creation with them, like: ${colors}_${fruits} - this would result in picking a random word from colors dict (let's say "red") and random word from fruits dict (let's say "banana"), resuling in someting like red_banana@mydomain.tld alias. It's ok if it worked only on custom (user provided) domain names, because of the potential lack of global naming variablity and even on the pro plan since it seems like a very specific feature and would require hosting user's dictionaries on the server.

Also thank you for creating this awesome service!