User-support category: works for anonymous, not for existing users

[Moin]

Category not accepting "anonymous email" from known users

Reproduce: Have a “private” category that only has create/reply/see access for members of a specific group. No other permissions. Enable “anonymous email in” for that specific via a unique working alias to the incoming POP account. Have a non-staff user that is not a member of the group send an email report in to the category email address from the email address associated with their account. Send in an email from an account not associated with any known Discourse account. Expected Behavior: …