DSN (Delivery Status Notification) is another name for the bounches. Basically, if the remote delivery fails, DONT send a bounce back to the sender.
Same domain = the domain the server is authorative for.
Basically, IF sender == "" and receiver != "*@yourdomain.com" then redirect to :blackhole:
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Från: Yves Goergen via Exim-users <exim-users@???>
Skickat: den 24 december 2020 10:45
Till: Sebastian Nielsen <sebastian@???>; 'Mailing List' <exim-users@???>
Ämne: Re: [exim] Forward from external immediately without queue
Do I have a DSN at all? Exim is doing the second delivery (forward) itself and fails itself, it is not sent a bounce back that it needs to forward.
Also, what is "the same domain"?
-Yves
-------- Ursprüngliche Nachricht --------
Von: Sebastian Nielsen via Exim-users <exim-users@???>
Gesendet: Donnerstag, 24. Dezember 2020, 10:22 MEZ
Betreff: [exim] Forward from external immediately without queue
Simple solution is to configure the server to not send any DSNs for forwards at all.
Since DSNs do have a blank sender, a trick is to have a router which detects a blank sender, and if receiver of the bounce isn't someone on the same domain, then blackholes it. (use :blackhole: as redirect data)
-----Ursprungligt meddelande-----
Från: Yves Goergen via Exim-users <exim-users@???>
Skickat: den 23 december 2020 20:34
Till: List: exim <exim-users@???>
Ämne: [exim] Forward from external immediately without queue
Hello,
I noticed in my log files that I have situations where some mail is received from externally which is supposed to be forwarded to externally (with the 'redirect' driver, or 'remote_smtp' transport?). Now if my spam filter didn't detect the message but it was rejected by the forward recipient, Exim will generate a bounce message and try to send it to an arbitrary sender which is mostly fake. This is causing backscatter, which may cause issues with my mail server reputation in general. (I know that the RFC requires that behaviour, but that RFC is broken and not practical, for well-known
reasons.) The same probably happens when the remote mailbox is full.
I tried to understand what the 'errors_to' directive does but it's hard to follow those descriptions. So I'm not sure whether it's useful in my case.
So I had another idea. If queuing and bouncing is the problem, can I get rid of that? If a message comes in from an unauthenticated sender, that must be another mail server. Those have got time, there's nobody waiting in front of a screen for the message to be submitted. So could Exim just try to deliver the message immediately in this case? If that fails, it could directly reject the message in the waiting original connection. No need for bounces.
If the remote error is permanent, so should be Exim's. Same for temporary errors. Passing back the remote error message is probably a privacy concern as it might disclose the forward address or provider.
This must only apply to forwards for unauthenticated senders.
Authenticated senders are my users, they provided a password and I know I can send them bounces safely. And they're waiting for completion of the submission.
How would a configuration of this look like? Or where in the documentation can I find more information about that?
-Yves
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