We have an unix email (user@A.com) which currently person used pop3 and smtp to retrive the email message . We have setup a new AD domain B.A.comand exchange 2007 server with domain (user@B.A.com), We would like to tryout first the exchange server 2007 berfore we fully migrate the mail system to exchange 2007, which is coexistence deployment, some user who has been setup the account on the exchange 2007 must received the email send user@A.com With the following scenario : 1. Exchange server 2007 will need to received email from internet user through current email server. 2. User who use exchange server 2007 will reply email using domain user@A.com How do I setup the followin configuration?? Based on my reading I can acchived it with 2 ways : 1. set the current mail served as a smart host for sending and receiving. 2. use a pop3 connector to retrieve current mailbox, but how about the sending? Thankskholil

More information on the concept of sharing SMTP namespace can be found here: http://technet.microsoft.com/en-us/library/bb124423(EXCHG.80).aspx http://support.microsoft.com/kb/321721 You can also see this post for more detail: http://forums.microsoft.com/TechNet/ShowPost.aspx?PostID=4052925&SiteID=17