Managing changes to legacyExchangeDN

by Shijaz Abdulla on 24.07.2008 at 16:37

If you had to change the legacyExchangeDN for your users as part of a migration or other manual process, or even an error in your automated user provisioning software, there are certain things that you need to be aware of.

For one thing, cached Outlook ‘autocomplete’ entries will stop working. If a sender uses his Outlook autocomplete to select a user whose legacyExchangeDN has been recently changedand sends an email to a user, chances are that the mail will bounce with the following NDR:

Jack Rabbit
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.

The first thing you need to do after changing the legacyExchangeDN is to initiate an Offline Address Book rebuild. The way out of this problem is to instruct the sender to first download the Address Book by doing a full Send/Receive. Then ask the sender to manually select the affected recipient from the Address book instead of using the cached Autocomplete.


This is because, in an Exchange organization, Outlook client autocomplete caches do not save the SMTP email address. Instead, it saves the X.500 address using the legacyExchangeDN attribute from Active Directory. And that’s exactly what you have changed!



There is another workaround to prevent the NDRs. This would be to enter the old value of the legacyExchangeDN attribute as an X.500 address for the user account. This is done by opening the user object’s Email Address properties –> Add a Custom Address –> Enter the old value of legacyExchangeDN as the address and the address type as "X500" without the quotes. The drawback of this method is that you are populating the user’s email address field with garbage, which you don’t need after a while but can’t remove because you are unsure if traces of the old entries in Outlook caches are gone!

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8 Responses to Managing changes to legacyExchangeDN

  1. Anonymous says:

    Hi Shijaz,

    You described clearly that how to solve legacy ExchangDN problm at client side. But, I am intersted to know that what to do on server to resolve this issue.

    Please inform if you update.


  2. Shijaz says:

    A manual change in legacyExchangeDN can be caused by a multitude of reasons – most often in migrations.

    However, in our case we had to manually modify the legacyExchangeDN because our automated user account provisioning software had a bug in it which resulted in the creation of user accounts with a syntactical error in the legacyExchangeDN attribute.

  3. Jim says:

    Hi Shijaz,

    Thanks for good description of autocomplete behaviour when LEDN is updated.

    Will LEDN update to AD contact cause NDR, where Exchange user attempts to reply to email from AD contact (and original email was sent before LEDN update)?

    I’m planning to use admodify to update LEDN for a batch of AD contacts.

    Thanks Jim.

  4. Shijaz says:

    Yes, it will cause NDRs when a user tries to reply/forward emails that were already sent with the old LEDN.

  5. Thank you so much for this post. That little trick with copying/pasting the old attribute contents into an X500 tag is really cool. I ran some tests and it works really well. This will allow me to fix some user accounts where the persons account was renamed from a former employee and the old employees name still shows up in Outlook when you are typing their name! Users HATE that!! Great topic, wish I found this a couple years ago. 😉

  6. Chris S. says:

    Perfect description of my problem. We import 12,000 students into exchange contacts for the last 5 years and their legacyexchangeDN started showing up with errors last week. We corrected the error but the problem still occurs if the user selects from the GAL. We tried creating a new outlook profile or deleteing the client history clear this, no luck.

  7. Andrew says:

    Hi Shijaz,

    We created some new OUs in which we moved some users from an older OU to another newly created OU and there after created a new sub-domain which we used to add new SMTP Address. Could this change cause a change to the LegacyExchngeDN? Because we’re constantly getting bounce backs.

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