i have an application that sends huge amount of buniness related emails to exchange server 2003 which forwards those eamils to ISP mail server using smart host for sending it to internet domains.

The over all process works find but the only issue we have is that we do not get the bounce back against invalid email addresses.our application is capable of fetching invalid email address from mailbox of sending ID, and mark these addresses as invalid directly in data base (based on SMTP error codes) .

ISP do provide us invalid email addresses report but it does not serve the purpose since marking invalid email address manually in data base is painful and prone to failures.

Note: when we use our mail server to directly send business emails to internet(NOT via ISP) every thing works fine, the sending process as well as the bounce back process. but using this setup leads to slow response of internal users so we cant use this permanently

any tip towards the solution(to recieve bounce back addresses) will be appriciated.

Hi Wahid,

Try to test with other ISPs, Connect wireless Internet datacard in that machine and send email. It will confirm us if there is issue with your current ISP or not.

Most likely, issue is with your ISP only.