Who picks it up — Preference first, then load

Two rules, in order. If the same customer has written before and their previous ticket's owner is on the roster, they get their usual person. That person is recognised by the address the message came from, so it works even when the ticket table has no customer relation at all. Otherwise the ticket goes to whoever has had the least work lately, measured over a window you choose, with ties broken stably rather than randomly. Assignment here is an offer of convenience, not an argument — it never overwrites a choice anybody made.