[Mimedefang] Am I overlooking something in my filter_relay method

ML Listuser listuser at ml-design.com
Sun Jul 16 12:24:17 EDT 2006


Thank you Jan-Pieter,

As a matter of fact I have a range smtp-vbrnn.xs4all.nl in the whitelist. I 
knew about xs4all as I often receive mail from there.
What I didn't knew/hoped was this behaviour from other ISP's. 
So this is typically something I overlooked.

I will see into John Rudd's suggestion.

kind regards, Frank


On Sunday 16 July 2006 12:37, Jan-Pieter Cornet wrote:
> On Sun, Jul 16, 2006 at 11:02:06AM +0200, ML Listuser wrote:
> > So I created a filter_relay which, on a connect-request, tries to
> > establish a telnet/smtp connection with the calling host and if it does
> > _not_ succeed, rejects the connection with '554 <my mx> ESMTP not
> > accepting messages'.
>
> You wouldn't be able to receive mail from us: xs4all.nl (and all
> customers and customer domains). Several other largish ISPs might
> have the same problem.
>
> Our outgoing smtp server is actually a loadbalancer, spreading
> the connections over several client machines. The client machines
> cannot receive incoming SMTP connections, since they are for outgoing
> SMTP only.
>
> This setup is not unusual, separating outgoing and incoming SMTP
> servers; And often the outgoing SMTP servers will not allow incoming
> connections.
>
> John Rudd's suggestion might make more sense, blocking on dynamic-
> looking hostnames. However that isn't ideal either, because it will
> block wellbehaved SOHO mailservers on DSL lines from really crappy
> providers (without properly functioning outgoing mailservers,
> and without a possibility to change the reverse DNS name).



More information about the MIMEDefang mailing list