OT: How do you block servers sending oversize messages?

[Ken A]

Why don't you put a box at some well fed colo somewhere else and filter 
incoming mail at that point? Given that 80% is spam anyway, you'd 
probably save quite a bit of bandwidth on your 64k frame. As long as you 
control the DNS you could switch back to your local box if you needed to.
Ken A.
Pacific.Net

Jim Holland wrote:
> This is a sendmail problem, but hope it's OK to ask here.
> 
> MANGO has only a 64k connection to the Internet.  We have a major problem 
> with ISPs (mainly Yahoo and Gmail) that don't implement the SMTP SIZE 
> extension.  So when they send us a 10 MB message, for example, we can't 
> reject the message until they have sent us the whole message.  That is a 
> total and serious waste of bandwidth, particularly when some idiot sends 
> us half a dozen 10 MB bmp files for example.
> 
> On our side we can see the incoming df file growing in size in mqueue.in,
> and can suspect from the sending server that it is going to be a problem,
> but obviously can't be sure until it hits our message size limit (1.5 MB).  
> At that point the df file stops increasing in size and we know it's a
> problem.
> 
> The manual solution at that point is to determine the sender's IP address,
> block that in the access file with an appropriate error message, kill the
> process id associated with the connection and then delete the df file.  
> Then wait until they next connect and get rejected, and then re-enable the
> IP in the access file once more (and hope that they don't do it all over 
> again).
> 
> The above response is definitely worth doing during our peak times as it
> frees up significant bandwidth.  I could (why don't I?) write a script to
> monitor and automate the process.  However the problem is fairly
> fundamental, and I wonder if others are concerned about this issue and
> whether they have solutions of their own.  
> 
> I have written to Gmail via a third party who knows the developers there
> and am told they will think about it and possibly implement an upgrade at
> some stage.  I don't know how to get hold of anyone interested at Yahoo.
> 
> Regards
> 
> Jim Holland
> System Administrator
> MANGO - Zimbabwe's non-profit e-mail service
>