Users with domains w/ postfix w/ recipient delimiter

I am migrating a set of domains from a host where every setting was custom hacked to a new more managed host using virtualmin. There are a couple of hard requirements for the move and two of them seem in conflict when receiving email.

Requirement 1: Usernames must be in user@domain.tld format
Requirement 2: The postfix recipient_delimiter must be . (a period)

I realize that the first requirement is a problem with postfix, but since virtualmin has the “extra user” workaround in place, that shouldn’t be an issue.

Virtualmin creates the extra user using this format: user@domain.tld => user-domain.tld. The postfix virtual tables then convert an email for user@domain.tld to user-domain.tld@hostdomain.tld

Oops. Since the host domain has a period as the recipient delimiter, postfix will look for a user called ‘user-domain@hostdomain.tld’ That user does not exist.

It looks like I can setup virtualmin to honor the first requirement OR the second requirement, but not both. Or am I missing something?

Is there some way to control the format of the extra user? This would work perfectly if the extra user was in the ‘user-domain-tld’ format.

There is a workaround for this, though far from ideal. I just manually renamed all instances of the user-domain.tld users in passwd, shadow, everywhere in /etc/virtualmin and any other place I found them. That does work.

On the downside, it does require that I make this change every new user I create. Also, the virtualmin user panes don’t recognize that this renamed extra user is a shadow of the main user and shows them as separate users. Maybe that’s related to RoundCube wanting to use the extra username as the default identity after the first login?