to: domain (id) important
Temporary queues
Created on the fly when a limit, a pause or greylisting holds mail back, and named after what is being held.
In detail
Not observed on our stand — nothing has been throttled there yet — so the naming pattern is taken from documentation and marked unverified. Their importance is out of proportion to their size: the sending queue is flat, with no per-domain breakdown anywhere, and these names are the only place the engine says which destinations are currently in trouble and how much mail is waiting behind each. A monitoring panel that lists them shows something no counter exposes.