"Delivery has failed to these recipients" - ExRecipNotFound error - Using Outlook 2010 - Can't send email to some email addresses of people in same domain - Exchange 2007, SBS 2010

Posted on 2011-10-05
Last Modified: 2012-05-12
I have SBS 2008 with Exchange 2007, also running DHCP and DNS.
My PC is running Outlook 2010.

My co-worker has two email addresses (eg and
Both domain names are managed by DNS on my SBS server.

If I send an email via outlook then Fred gets emails to but not
When sending to I immediatedly get an Undeliverable email response showing this error:

" Delivery has failed to these recipients or distribution lists: Fred Bloggs ( The recipient's e-mail address was not found in the recipient's e-mail system.... etc ... etc.... #550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ## "

Now here is the strange thing... if I use web mail (eg https://mysbsserver/owa) then he gets both emails.

go figure - what is Outlook 2010 doing to trick exchange into doing this???
Question by:enigmasolutions
    LVL 5

    Expert Comment

    Often will happen if the PC has another cached value for the contact you're sending to.

    When you start to type the email address, do you get an autocomplete filling it in?  If so delete the autocomplete entry and try again.

    If the address is in the contact - same thing, correct or delete the address.

    Be sure to type out the full email address when testing again.
    LVL 1

    Author Comment

    Thanks.  I tried it ... but it didn't work.
    LVL 1

    Author Comment

    Hmmm interesting.... I have been runnign a few threads in E-E and got the sugestion to run "Fix my network" with the results as shown.

    It says "A suggested port mapping is missing on your router that allows e-mail or Web traffic through the firewall".

    I don't get this... I mean I have SMTP port 25 mapped to my SBS server.  I also have HTTPS port 443 mapped to my SBS server.

     Fix my network screen shot
    LVL 1

    Author Comment

    BTW - not sure if my comment above is relevant - just thought I would throw it in...
    LVL 5

    Accepted Solution

    Don't think it is.  You say both domain names are managed by DNS.  Is the Exchange box aware that it is responsible for both?  If not, it will just try to forward email to a non-internal address to an outside domain and get lost.  That wouldn't fit with the OWA or the firewall issues unless it is somehow forwarding out and back to itself.

    Has/does this work for anyone else?
    LVL 1

    Assisted Solution

    Yes Exchange box was aware that it manages DNS and domain names.

    We managed to fix our problem.

    In fact our SBS server was in a bit of a mess with multiple problems.

    I posted a separate question for one of the other problems here

    Rob and Jarred helped a great deal.  But even after all the good work done by Rob and Jarred, it was my local MSCE who finally fixed all the problems.  

    Anyway I have invited him to provide a brief description of how he fixed the problems.
    LVL 1

    Author Closing Comment

    I regret not probiding more details on how we solved the problem.  The fact is I have lost track of all the changes we made.  

    We also experienced some bizarre problems with our router - see here

    Anyway thansk for your help.

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