On 10/12/2013 3:43 AM, Noel Butler wrote:
On 12/10/2013 19:22, Daniel Parthey wrote:
No mail will be lost, since it should remain in the remote MTA's mail queue for a while in order to be retried and delivered later.
No guarantee there, some services are broken and do not retry, hotmail used to, and I've heard in some cases, still does, do this, some marketing system (ok, so thats no loss) do this - there reasoning is because of such high outbound queues, it would only delay first runs and upset their clients, again, no loss to me, but one persons spam can be anothers ham.
It is after all why we have secondary MX's, on network, and if need be, off network.
Instead of deferring the message and returning a 4xx to the remote client, accept it normally and put it into a hold queue or defer the delivery transport. After the switchover, requeue the message.