[exim] How to limit to authenticate user to send mails per H…

Hi All,

I am really frustrated as some spammers pick and id password from my server
and sends lot of mail to change from id like if the stole id and password
of abc@??? the they send lot of mails to user from mail id
as@???, ad@??? and so on to use the is auth id and password
of abc@???.

Please help me to short out this.
thank all in advance.