A professor I know is becoming head of department, do I send congratulations or condolences? I don't know much more about the transition - only that the professor is becoming the new head effective [date], and that they have the support of the department.
Do I send congratulations (because it's a promotion) or condolences (because apparently some professors don't actually want the promotion, and only become the head of department reluctantly)?
Edit: what about the outgoing head of department? I clearly shouldn't send condolences in that case, but should I send congratulations?
That would depend on how well I knew the person. If they were a very close friend of long standing, I'd probably offer condolences, just as a joke. But that would take a special relationship.
In the general case, only congratulations are in order.