Exchange 2007 error - 550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found

Posted on 2011-10-04
Last Modified: 2012-05-12
We migrated from Win 2003 with Exchange 2003
to SBS 2008 with Exchange 2007.

Now we get this error every time a user sends an email to another user within our domain.
External emails are OK.

Also getting a "connect to sites" prompt asking for a user name and password every time we do anything in outlook (eg start outlook or send email).

My DNS looks like this - have I set it up wrongly?
(computer names obsucred for security reasons)

 DNS Setup
Question by:enigmasolutions
    LVL 16

    Accepted Solution

    Make sure Exchange 2007 service Pack 3 installed on the server

    There was an issue with repeated password prompts that was resolved by installing Rollup 9 for Exchange 2007 SP1, however I would recommend that you should now be using Exchange 2007 SP3

    Ref :
    LVL 1

    Author Comment

    FYI - My primary problem was caused by having several email addresses and domains for some of my co-workers that were not transferred to the new server (eg,,, But the guy who set up exchange forgot to create email addesses for all of them.  Quite simply I was sending an email to one of these addresses that wasn't linked to any user.

    The "connect to sites" could have been resolved by the SP3 upgrade.

    But, I was using Outlook 2007 and before I did the SP3 upgrade, I upgraded outlook on my PC from 2007 to 2010 and I think this seemed to fix the problem.  

    Actually I didn't really test it much before I also applied the SP3.  So who knows?  You were probably right anyway.

    Anyway.  A big thank you for your response.

    LVL 1

    Author Closing Comment

    Whilst my own solutions was the correct answer on this occasion, I suspect that upgrading to SP3 may have also helped.

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