On 2015-05-14, Rob Gunther <redrob@???> wrote: > Looks like I figured out part of the issue. The destination server is
> refusing to accept mail from some of our Exim servers. They have their
> Exchange connector locked down so we get this on some connections:
>
> *421 4.3.2 Service not available, closing transmission channel*
>
> So at some point Exim records in its internal systems that it is not
> possible to deliver to that server and will stop trying totally?
Now that messages have been on he queue so long that exim is
discarding them undelivered it will not accept messages for that
destintion. It won't stop entirely. When the retry clock for that
destination expires it will retry with either a new message or one
from the queue. until then it will reject new messages.
