[Greylist-users] SMTP/AUTH before greylist problem

William Blunn bill--greylist at tao-group.com
Thu Aug 4 03:32:04 PDT 2005

Dave Warren wrote:

> No -- The problem is that *every single time* they configure their 
> mail client they have to change the port from 25 to 587.  This results 
> in a support cost every time a user needs their client configured.
> My instructions have used 587 since the day I added support on my mail 
> server, but most people still use 25 because they simply don't bother 
> to go into the Advanced options to configure anything even if the 
> instructions tell them to do so.

You could block TCP connections to port 25 for hosts inside your 
network. That would force people to configure correctly from day one.

Better yet, you could put in a networking rule so that TCP connections 
to port 25 originating inside your network are redirected to port 587?

Under netfilter that ought to be something like:

  iptables -t nat -A PREROUTING -s $mynetwork -p tcp --dport smtp  -j 
REDIRECT --to-port 587

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