Author: Jeremy Harris Date: To: exim-dev Subject: Re: [exim-dev] [Bug 1253] New: Messages rejected with 421 are
delivered
On 24/05/2012 11:06, Alex Frolkin wrote: > 1. Start Exim.
> 2. While Exim is running, chown mainlog and rejectlog to, say, root, so that
> Exim can't write to them.
> 3. Try to deliver a mail from a remote machine via the local Exim, via SMTP.
> 4. Exim will respond with "421<hostname> Unexpected failure, please try later
> - closing connection." after end of DATA.
> 5. However, the message will still end up on the queue and will get delivered
> on the next queue run, by the looks of things.
>
> Obviously, this has the effect of sending out multiple copies of the same
> message, one for each retry after a 421.
As far as I know there's a fundemental issue with the balance between
the chance of mistakenly dropping a mail and the chance of duplicating
one. Consider what happens when a final data ack gets lost. Most mail
software prefers to err on the side of duplication and Exim is no exception.
Unless you think that the misconfiguration is likely to be a common one,
I don't think we'd want to make changes to accomodate it.
