I have SBS 2008, Exchange 2007.I now need to add a seconary domain.e.g. The primary domain is foo.com, the secondary domain is bar.comI have added bar.com as an accepted, authoritative domain.I have edited the SBS Email Address policy and added @bar.comUser mailboxes now have e-mail addresses in the form user@foo.com and user@bar.comHowever, if I attempt to use outlook to send mail from user@bar.com via exchange, I get an undeliverable message:"You are not allowed to send this message because you are trying to send on behalf of another sender without permission to do so. Please verify that you are sending on behalf of the correct sender, or ask your system administrator to help you get the required permission." I have no problem sending via the primary domain but, how do I allow users to send via both user@foo.com and user@bar.com ?I've followed a number of suggestions on this site to resolve this issue but so far, without success.db

You can assign secndary addresses to a mailbox and it will receive email addressed to any of those addresses, but you can only send email from the primary SMTP address. There are some third party programs that will enable this, or you can create new dummy user accounts and new mailboxes for all the users you want to enable for both addresses, make the .bar addresses their priimary smtp address and give the user with the matching .foo address Send As permissions to that user.

Thanks for this - not quite waht I had hoped for - but I'll give it a trydb

....or you can create new dummy user accounts and new mailboxes for all the users you want to enable for both addresses, make the .bar addresses their priimary smtp address and give the user with the matching .foo address Send As permissions to that user. Ok, I have now tried this Primary domain foo.comSecondary domain bar.com added as accepted domainNew SBS Email Address policy for @bar.comNew user 'john@bar.com'Assigned send as permission for john@bar.com to john@foo.com.. I still have the same problem..."You are not allowed to send this message because you are trying to send on behalf of another sender without permission to do so. Please verify that you are sending on behalf of the correct sender, or ask your system administrator to help you get the required permission." This is despite having explicitly granted the permissionwhere am I going wrong?db

You may need to wait a bit. Send-As permissions have to replicate from AD, and that process runs on a 2 hour interval.

Hi, You can also configure POP3 for the user@bar.com to work around this issue. Thanks Allen