Dear Techi Guys Around the Globe, We face a very strange problem , we have exchange server 2007 which is running in a win 2008 server. we are not able to receive emails from some domains , strangely we can send emails to those domains but not able to receive emails. The bounce back message which the sender receives is : 'Your message did not reach some or all of the intended recipients.550 5.1.1 unknown or illegal alias' Any workouts for this issue ?....ur expert opinion and thoughts will be highly appreciated. Thanks for your time !!

Ask them to give you full mail headers so you can clearly see what is going on , maybe they are mistyping the recipient e-mail address , as error indicates the valid SMTP proxy address is expected on SMTP handshake someone@domain.com 550 5.1.1 unknown or illegal alias' You can also post here the full headers as well for us to take a look ocd