On Wed, Jul 10, 2024 at 07:44:05PM +0200, Steffen Nurpmeso via Postfix-users
wrote:
> Well, i do not know, .. but i have
>
> message_size_limit = 500000
Wow, that's rather restrictive in age when disk capacities are starting
to be measured in 10s of terabytes, while the majority of mail servers
already allowed ~10MB back when 10s of Gigabytes was a plausible disk
size. Do you do a lot of time-travel to the 1990's? :-)
https://commons.wikimedia.org/wiki/File:Hard_drive_capacity_over_time.png
> (Btw, does the client part of RFC 1870 actually exist in practice?
Yes, definitely. Many (though not all) sending MTAs use
MAIL FROM:<envelope-sender> SIZE=...
and bounce the large messages over the declared size limit without even
sending "MAIL FROM:" when the size limit in the EHLO response is
smaller.
> I cannot recall to have seen it. Does postfix log such client
> declarations? Would not think it does..)
No, the client's "MAIL FROM" is not logged at that level of detail, only
the envelope sender is logged by the queue manager when messages enter
the active queue, and by that time it may already have been rewritten.
>
> I have a problem in that I would like several senders to be able
> to send larger messages.
You may as well advertise the largest supported size, it is better
better than advertising just "SIZE", because clients that honour
"SIZE=<limit>", but don't send "SIZE=" in mail from will be able to
avoid attemting transmission of overly large messages.
> Letting aside the "extended MAIL" client command that i never have
> seen, what i would hope for would be that postfix simply says
>
> 250-SIZE
There's little to gain by doing that. Instead, just advertise the
absolute ceiling.
>
> and would then have something like a lookup table that allows to
> configure the actually used size limit based upon senders.
> Is this somehow doable?
That's where your policy service comes in. It can check the envelope
sender address and act accordingly. Perform the check both in:
smtpd_data_restrictions and smtpd_end_of_data_restrictions. The
former will check any "SIZE=" value promised by the client, while
the latter will check the actual received message size.
Postfix has no built-in sender-specific size enforcement, and none is
needed, given the policy service mechanism. IIRC milters get to see
the full extended "MAIL FROM" command, and the message content, so
you can probably use a milter if you prefer, but a policy service
feels simpler.
--
Viktor.
_______________________________________________
Postfix-users mailing list -- postfix-users@postfix.org
To unsubscribe send an email to postfix-users-le...@postfix.org
