dovecot - Apr 2007 - Deferring, instead of rejecting, messages when at quota

Greetings -

I'm having trouble working out where to alter this behaviour (so  
please forgive me if it turns out to be an Exim thing rather than  
Dovecot!)...

My test service is using Exim as the MTA and Dovecot's "deliver"
for
the LDA.  We are using Maildir mailboxes with filestore quotas.

When I send a large test message to myself that cannot be delivered  
because I don't have sufficient available quota remaining an error  
message is immediately returned to the sender and the incoming  
message discarded.  The error message says this:

     Your message was automatically rejected by Dovecot Mail Delivery  
Agent.

     The following reason was given:
     Not enough disk space

Instead of Exim rejecting the incoming message and generating the  
error response because of deliver's failure to, umm, deliver I'd like  
the message to be retained in Exim's queue so that it can be retried  
periodically.

With our old/live system (Sendmail + UW IMAP's "tmail" LDA) I
edited
the tmail source code to return a different exit code: one that  
caused Sendmail to defer (re-queue) the message rather than reject it.

How do I achieve this effect with Exim + deliver please?
Is it a case of:

   * Setting something in Dovecot's configuration file (I can't spot  
what!);

   * Changing a return code in deliver's source (if so, whereabouts  
and to what?);

   * Or is there an Exim directive I need to add to the transport  
definition in
     its configuration file?

With thanks,
Mike B-)

-- 
The Computing Service, University of York, Heslington, York Yo10 5DD, UK
Tel:+44-1904-433811  FAX:+44-1904-433740

* Unsolicited commercial e-mail is NOT welcome at this e-mail address. *

On Thursday 26 April 2007 11:17, Mike Brudenell wrote:
> When I send a large test message to myself that cannot be delivered
> because I don't have sufficient available quota remaining an error
> message is immediately returned to the sender and the incoming
> message discarded.  The error message says this:
>
>      Your message was automatically rejected by Dovecot Mail Delivery
> Agent.
>
>      The following reason was given:
>      Not enough disk space
>
> Instead of Exim rejecting the incoming message and generating the
> error response because of deliver's failure to, umm, deliver I'd
like
> the message to be retained in Exim's queue so that it can be retried
> periodically.
>
> How do I achieve this effect with Exim + deliver please?
In Exim, you can set the temp_errors option of the transport. I don't know 
what code is returned in this case, but I have temp_errors = 73:75:77:78:89. 
If Exim takes care of all the hard errors (like nonexisting user...) you can 
almost set temp_errors = *.

-- 
Magnus Holmgren        holmgren at lysator.liu.se
                       (No Cc of list mail needed, thanks)

  "Exim is better at being younger, whereas sendmail is better for 
   Scrabble (50 point bonus for clearing your rack)" -- Dave Evans
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Greetings -

On 26 Apr 2007, at 10:36, Magnus Holmgren wrote:
> In Exim, you can set the temp_errors option of the transport. I  
> don't know
> what code is returned in this case, but I have temp_errors =  
> 73:75:77:78:89.
> If Exim takes care of all the hard errors (like nonexisting  
> user...) you can
> almost set temp_errors = *.
Hmmm... I'm continuing to peer at the source code of Dovecot's  
deliver and related libraries and have a feeling it's not going to be  
as straight forward as the above.

It looks as though deliver calls routines in lib-storage to try and  
write out the message.  If these detect a problem they flag the  
error, and the routine they use to do so indicates it is not a  
temporary one.  Deliver sees the write failed and, seeing that  
temporary_error is FALSE itself generates and sends the error response.

I'm currently trying to work out how this behaviour can be changed  
without affecting other things.

For example it probably isn't safe to change the function used by the  
storage routines to flag that any and every error logged through it  
is a temporary_error: there may well be other places it gets called  
where the error is NOT temporary.

Likewise I'm not sure if I can simply change the source of deliver to  
always return a temporary failure code because again there may be  
other problems that occur which should be permanently failed.

I think I need help from Timo on this one, unless someone has already  
worked this one out previously?

Cheers,
Mike B-)

-- 
The Computing Service, University of York, Heslington, York Yo10 5DD, UK
Tel:+44-1904-433811  FAX:+44-1904-433740

* Unsolicited commercial e-mail is NOT welcome at this e-mail address. *