We have an environment that we have just migrated to Exchange 2007. Right now we have it coexisting with Exchange 2003. There are some internal scripts that were set up by development that email directly to alias accounts in 2003 but now that we have moved that department to 2007 the mails no longer deliver and give the following message (names changed for privacy):>Generating server: exchange2.corp.domain.com>>alias@domain.com>#550 5.1.1 RESOLVER.ADR.RecipNotFound; not found ##>>Original message headers:>>Received: from exchange2.corp.domain.com ([10.xxx.x.xx]) by> exchange2.corp.domain.com ([10.xxx.x.xx]) with mapi; Mon, 18 Aug 2008> 11:33:59 -0600>Content-Type: application/ms-tnef; name="winmail.dat">Content-Transfer-Encoding: binary>From: User Corky<ucorky@domain.com>>To: "user@domain.com" <user@domain.com>>Date: Mon, 18 Aug 2008 11:33:58 -0600The only way I could resolve this was to go in and add 2 SMTP addresses for the accounts the mail is set to. I can not see having to do this for all the users.Does 2007 not allow alias deliveries ? This is affecting all groups and distros as well.Thanks for any help.EJ

What do you mean by "alias accounts"? Were you using un-migrated contact objects to forward email to other objects?

Hi, Numeric Code: 5.1.1 indicates that the recipient address is invalid or does not exist in the directory of the recipient email-system. So first please check whether the alias account has mail enabled. Please try to find the mailbox in Exchange Management Console-Recipient Configuration-Mailbox. Besides, please follow the below article to reset the Outlook nickname cache to avoid any nickname corrupting issue. How to reset the nickname and the automatic completion caches in Outlook http://support.microsoft.com/kb/287623/en-us BTW, what is your Exchange scenario before you install exchange 2007 into the org, has smart host? What did you mean email directly to alias accounts in 2003?these account do not has mailbox? More information share with you: How to Configure Authoritative Domains for the Exchange Organization http://technet.microsoft.com/en-us/library/bb124907.aspx Managing Accepted Domains http://technet.microsoft.com/en-us/library/bb124423(EXCHG.80).aspx Managing E-Mail Address Policies http://technet.microsoft.com/en-us/library/aa998940(EXCHG.80).aspx Hope it helps. Xiu

Jeff, yes that's what we are doing. Initially the email accounts are generated with the standard naming convention for the company and an alias is assigned to the account afterwards. They had been using a mail gateway to deliver the messages, and since it was in 2003 it worked fine. No one here seems to be able to explian to me what this gateway does, where it resides or who manages it.With the mailboxes that have moved over to 2007 we can no longer send to those "alias" email addresses without manually adding new SMTP addresses. I know there has to be a way to do that with relay or forwarding but not exactly sure how to go about it. I do not want to have to manually enter these new SMTP addresses as we migrate since we aren't even sure what accounts are being used. I am coming in very new to the company and have just started the migration.I am confused on the second answer, the NDR is deceiving.