how to stop using *telnet <domain> 25*

[Matthew Carpenter]

Swapana Ghosh wrote:

>Hi
>
>--- Bill Campbell <linux-sxs at celestial.com> wrote:
>  
>
>>On Fri, Jan 23, 2004, Swapana Ghosh wrote:
>>...
>>    
>>
> 
> (b) it would prevent your own roaming users
>  
>
>>from sending mail from outside your network.
>>
>>    
>>
> 
>Yes that is the main problem. We can't stop any users mails. By the way
>*telnet* port is closed for all our servers -  that is from our server level, 
>but how to stop others from telnet and using port 25.
>
>Thanks again
>-Swapna
>
>
>  
>
if you know the IP Address:

iptables -A FORWARD -p tcp -s 192.168.2.52 --dport 25 -j DROP

should work....  But that will stop him from sending email to/through 
the server altogether (email client or otherwise) unless some other 
transport is set up, like SSL on port 465.