I can put that stronger: I've either worked on or read the source of seven programs/libraries that will send EAI mail, and I don't think any of the seven would be able to fall back to an alternative address.
That sort of fallback mostly makes sense in a webmail system where the MTA and MSA and address book are sufficiently integrated. To do it in postfix or exim you'd need to add an MTA-side address book of aliases which is rather unlike anything they do now. I use qmail which can easily tell whether addresses A and B deliver to the same place, but cannot tell you the other addresses that deliver the same as A, which is what you need here. Regards, John Levine, johnl@iecc.com, Primary Perpetrator of "The Internet for Dummies", Please consider the environment before reading this e-mail. https://jl.ly