causes all mail queued for that host, no matter what domain its for, to be dequeued. Why doesn Exim support this?
A0521: Exim does not keep queues of mail for specific destinations. It just keeps one pool of undelivered messages. What is more, once you start a delivery of a message, it tries to deliver to all the addresses in the message, not just the one you may be interested in. (Of course, this doesn’t usually do any harm.) The only way it could be done within Exim would be, for every message on the queue, to go through the motions of routing each undelivered address and see if that resulted in a delivery to the host of interest. This could be extremely expensive (e.g. 1,000 messages on the queue, only 1 for the given host). The bottom line is that Exim just wasn’t designed for this kind of operation, that is, holding messages for intermittently connected hosts. The queueing arrangements are designed for handling delivery problems that are not expected to be common. A better way to do this is to implement the required queues separately. After all, keeping such mail on an “active” queue (where E
