IMCEAEX i NDR

 This problem is not common but quite annoying and usually hard to understood by users.

In most cases problem occurs If you remove mailbox and re-create it with the same AD account , for an example after firing and  re-hiring of the employee after some time.

It also occurs after migrations.

When user sends an email to a recipient, to which earlier messages was delivered without any problem. Sudennly gets an Non Delivery Report with this content:

Delivery has failed to these recipients or distribution lists::

Test User

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..

Diagnostic information for administrators:

Generating server: server01.exchange

IMCEAEX_O=Company_OU=EXCHANGE+20ADMINISTRATIVE+20GROUP+20+28FYDIBOHF23SPDLT29_CN=RECIPIENTS_CN=user@xxx.xx
#550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##

And now the question is: Why?

Mailbox exists , got a valid SMTP address, emails from other senders are delivered without any problems …

The trail leads to Outlook and auto completion of addresses. In the cache of sender’s Outlook  is stored a old recipient address. When addressing a message, Outlook automatically suggests the address to which was  previously sent messages.

For a internal addresses Outlook uses LegacyExchangeDN, and these addresses are stored in Outlook cache. And our recipient has the same SMTP addres , but different LegacyExchangeDN

What is the way out of this situation?

The easiest solution is to delete an old entry from Outlook suggested contacts.

Reselecting recipient  from GAL or manual typing address will save correct LegacyExchangeDN to Outlook cache. And the problem wil be solved.

Well, yes but this solution is a bit annoying for users. and, not really works well with a larger number of affected senders.

Second option is to add old legacyExchangeDN as a X500 address to the new mailbox.

In proactive approach we should write down and save this atribute. We can check this with folowing command:

Get-Mailbox user |fl legacyExchangeDN

But usually we do not have such information.

In this case, we can reconstruct the address from NDR.

IMCEAEX_O=Company_OU=EXCHANGE+20ADMINISTRATIVE+20GROUP+20+28FYDIBOHF23SPDLT29_CN=RECIPIENTS_CN=user@xxx.xx

And the X500 address will be look like:

/o=Company/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=user

如上内容来自博客：http://exchangeblog.pl/