Re: [Exim] Feature request: defer_once ACL (and local_scan) …

> I'd like to have a method to allow Exim to return a 4xx temporary
> failure to a mail only _once_. If a defer_once result is obtained for a
> message which has already been seen (using Message-ID as a key and maybe
> md5sum of body if there's no Message-ID), the message should be
> accepted.

Exim always adds message-id if there's not one. I don't know if that ID is
available to DATA acl or not.

> I'd use this in conjunction with content filtering. Those mails which
> are only _slightly_ suspicious can be deferred once and if the sender
> makes a second attempt to deliver them, we're then slightly more
> inclined to believe it's a genuine mail.
>
> I know it can be hacked up with SpamAssassin and sa-exim, but I think
> it'd be a lot cleaner and more generally useful if Exim could do it for
> itself.

So, if someone sends you a 5mb message, you defer it, then they attempt
again, you accept it. Sounds like you're going to double your incoming
bandwidth if you check it after the message is received.

I thought about defering all message in the rcpt (except ones I know are
100% valid) and accepting them later. Problem with that is, if someone
sends 2 seperate messages via the same host with the same sender/recipient
combination, it would accept the 2nd one.

If you have bandwidth to spare... =)

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