Let's say we are aceppting emails for the two domains wine-and-cheese.com and beer-and-pretzels.com.
I plan to create two mailboxes info@wine-and-cheese.com and info@beer-and-pretzels.com.
By default, the local part of the SMTP address uses the alias, which is the same as the sAMAccountName. Since I cannot have two AD users with the same sAMAccountName, I choose to name them "info-wine" and "info-beer". The result is, that I have two mailboxes with the address info-wine@wine-and-cheese.com and info-beer@beer-and-pretzels.com, respectively.
One thing I could think of would be to manually add info@wine-and-cheese.com and info@beer-and-pretzels.com to the corresponding mailboxes. I prefer to avoid anything that has to be done manually.
Another idea, that involves manual editing is, to change the aliases of both mailboxes to "info", but that results in having the second mailbox create the SMTP address info2@….
I am very interested how you handle those situations, particularly in bigger companies with more than 50 employees and 75 mailboxes.