huge mail going throw my mail server how to protect

[Joe Zeff]

On 04/06/2012 12:28 AM, Rafiqul Islam wrote:
> My question is too many unknown user sending mail using my MTA(Postfix)
> so that hotmail,google reject mail from my domain(mail.navigation.com
> <http://mail.navigation.com> and IP:202.53.168.75)  and i don't know how
> to stop this unexpected outgoing mail.

Close incoming Port 25 and tell sendmail to accept mail only from 
127.0.0.0.  HTH, HAND.