Re: [exim] exim 4.96 stopping because postfix is starting?

On 20/12/2022 20:40, Johnnie W Adams via Exim-users wrote:
> In this particular case, the message is not deliverable because the address
> no longer exists--but how would I know that if I hadn't seen the bounce
> message? I have to learn that at some point in the cycle.

Assuming this "you" with an Exim hat on rather than a sysadmin,
you find out when you try to deliver it. That probably means
"in the routers chain" specifically.

Routing has to be done for delivery; it's how exim decides where
to deliver to. But: you can ask for a additional run of the
routing from an ACL which is run earlier, before you agree
to accept the message from the sender and while the SMTP connection
is still open. Based on that routing failing (here, because the
user account does not exist) you can reject the message.
Since it was never accepted, there is no need to generate a bounce
to tell the alleged sender; you just told the using the SMTP reject.

This is called "recipient verification". I suggest you look it
up in the Exim documentation.
--
Cheers,
Jeremy