Exchange NDR when sending to active user

Some (but not all) of my users are getting the following NDR when trying to email a user:

Fred Jones
The recipient's e-mail address was not found in the recipient's e-mail system. Microsoft Exchange will not try to redeliver this message for you. Please check the e-mail address and try resending this message, or provide the following diagnostic text to your system administrator. 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##

Fred Jones ( is a valid address though which is strange. And, like I said, some users can email him fine.

Can anyone shed any light on this? Running Exchange 2007/ Outlook.
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Alan HardistyCo-OwnerCommented:
Okay - plan B!

Add a new Email Address to the users Account - but don't add an SMTP address, add a Custom Address, Type in 'X500' (minus the quote marks) as the Type and


as the address.  That should resolve the issue.
Alan HardistyCo-OwnerCommented:
he problem here is likely that the people sending the mail that is getting rejected are using the auto-complete address which is cached in Outlook but that the user has changed on the Exchange Server and the Autocomplete cache has not been updated, so it is trying to send to the wrong internal address and this is being rejected.

If the senders type in the full email address (not using autocomplete), or pick the address from the GAL, can they send happily?

If so - get them to delete the entry from the autocomplete by starting to send a new message, start typing the recipient address then selecting the entry that corresponds to the right user from the list using the up and down cursor keys, then pressing the Delete key.

Should be problem solved.
kam_ukAuthor Commented:
Tried it on my laptop, which was having the problem...yes, if I pick from GAL, then the email goes through fine.

Is this the only fix though, from the client side? Is there anything I can do on the server to fix this?
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Alan HardistyCo-OwnerCommented:
The problem is out-of-date cached information on the client(s).  You could globally remove everyone's .NK2 files when they login, but that would be overkill for a few internal address and you would also lose any other good addresses that your users might not have saved in their contacts.

I presume the user that was being emailed and was generating the NDR was moved internally?
kam_ukAuthor Commented:
I'm not sure what happened to the user, they just returned from a break from the company and I thought they had been given their old mailbox and AD account back. Possibly these users getting the NDR are trying to send to a cached entry for this name, I know that's the case for me.

Can I redirect his 'old' address to his new one in anyway, set some sort of forwarding?

Alan HardistyCo-OwnerCommented:
The problem is the LegacyExchangeDN attribute on the user's account.  You could change the attribute using ADSIEDIT to match the entry in your question but anyone who has emailed the user and cached the existing LegacyExchangeDN value, would then have the same problem although you would have fixed the existing users problems.

Short answer would be to advise your users of the problem and how to correct it, then let time heal the problem.
Alan HardistyCo-OwnerCommented:
Obviously change the part to reflect your domain name that you obscured.
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