Re: [EXIM] Temporary errors during SMTP transport

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Author: Georg v.Zezschwitz
Date:  
To: Philip Hazel
CC: exim-users
Subject: Re: [EXIM] Temporary errors during SMTP transport
Hello,


I consider your plans to be a brilliant idea that would perfectly
help with some of the most recent problems we have:

- Customers with Mailservers that have a per-user-quota and
send a braindead 4xx-response to the "RCPT TO: <username@..>"
request

- Braindead MTAs and Firewalls that will timeout after the '.'-
command, if the E-Mail contains a '\0' at the end:
E.g. they would not recognize 'Bye, John\0\n.\n' as a valid
end of the DATA-section.
Braindead in this meaning are:

    - StarGate
    - WatchGuard Firewall


- A very silly Firewall SMTP-Implementation that tries to limit
the incoming mail size by "interrupting" the connection.
(Yes, it just drops the connection at x MB. This is really
good for ISPs having a volumne-based charge)
Beneath the traffic, other messages get stuck behind the
big one.


A few comments:

> (B) A message error is associated with a particular message when sent to a 
>     particular host, but not with a particular recipient of the message. The 
>     message errors are:

>
>     . Any error response code to MAIL FROM, DATA, or "."
>     . Timeout after MAIL FROM



. SIZE-feature in EHLO-response with a SIZE below the message size
. Timeout after DATA
(See above)

>
> (C) A recipient error is associated with a particular recipient of a message. 
>     The recipient errors are:

>
>     . Any error response to RCPT TO 
>     . Timeout after RCPT TO

>
>     A permanent error response (5xx) causes the recipient address to be 
>     failed, and a delivery error report to be returned to the sender. A 
>     temporary error or a timeout causes routing retry data to be created for
>     the failing address. 
>     This means that the address will not be processed 
>     again, in any message, until its retry time arrives.

            ****************


I think this policy is acceptable, but this might be possible:

MAIL FROM: <mailing@???> SIZE=<the size is BIIIG>
250 You are welcome
RCPT TO: <gvz@???>
250 O.k., Georg love's to get big mails
RCPT TO: <poorboy@???>
420-Sorry, this user just has a 10 MB-POP3-box, your mail does not
420-fit in at the moment...

poorboy will get no further messages from us, till his retry time
is reached...



Greetings,


Georg

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