Exchange Server X500 Address An Amazing Thing to Know

In Exchange Server we are familiar with SMTP Address like of them are happy with just one or two of SMTP Addresses. But what happened if you have migrated any user , setup cross forest , just try to Reply in someone who left from the company or face a mailbox corruption and must create the same mailbox? Then probably you will see some strange behaviour of the email address.

Previous month i face the same behaviour when I decide to delete all the Contacts from our Exchange Server and import again only same Contacts which active and some new Contacts . Next day all my users start to complain that when send emails in email addresses of contacts return an Undeliver email. This situation happened only for the email addresses of contacts that has imported previous day.

Then I realize that i have done a terrible mistake that can't resolve it. The problem created when delete all the contacts  and recreate again the same contacts and new one. This problem occurs because while the Outlook auto-complete cache stores SMTP addresses for e-mail sent to external addresses, it uses X.500 addresses for e-mail sent to addresses within the Exchange organisation. Even though we had given the conact or user account all the old SMTP addresses, the old X.500 address which Outlook was sending to was missing. So this cause exchange to reject the message and return and undeliver email like

Delivery has failed to these recipients or groups:
Kostas Example
The e-mail address you entered couldn't be found. Please check the recipient's e-mail address and try to resend the message. If the problem continues, please contact your helpdesk. 
Diagnostic information for administrators:
Generating server: 
#550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##
Original message headers:.................


I done my research  for X.500 address and i realize that is amazing what can do and resolve the problem. So let's start to explain step by step how can create a new X500 Address in the Exchange Server and avoid the problem of Undeliver Email when user try to send it from Outlook autocoplete list.

My scenario related with the Mailbox contacts of Exchange Server but this doesn't mean that you can't use it with email address of a mailbox.

  • If you have delete the mailbox or contact(in this scenario) this is the most important step because you must have a backup to continue. ​If you don't have then you can't do anything.
    As IT Pro you will take care about Backup but in case that you inetresting to change it you can read some of my Reviews for Backup Softwares like

Altaro VM Backup Review
Vembu BDR Review -Installing and Configure Backups
Nakivo Backup & Replication  v7 Review or explore Category of Reviews for more details.

  • After restore the old conatct (for my scenario) or the user in other cases login to the Domain Controller
  • In the case of more than few contacts or mailboxes then read Export List of Emails Addresses from Exchange Server  to export Reports in minute that can help you .
  • Open the Active Directory Users and Computers and locate the Organization Unit which have all the Contacts.

  • Find the contact which restore (in this example the Display Name is kostas) and Right Click - - > Properties.

  • Select the Tab Attribute Editor and find the attribute legacyExchangeDN.

  • Double Click in the attribute and the value will be like
    /o=EX Organization/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=kostas214

  • Copy the value in a notepad.
  • Connect in the Exchange Server and go in Recipient Configuration - - > Mail Contact

  • Find the contact which have restore (in my scenario the display name of contact is Kostas) Right Click - - >Properties.
  • Select the Tab E-mail Addresses .

  • Click in Add Button and select Custom Address...

  • In the E-mail type write X500.
  • In the E-mail Address Paste the Value which copy from User in Active Directory.

  • Click OK and OK.

Now you must wait until  Exchange Server Update the Offline Address Book and push all the changes in the Outlook users. If you use Exchange Server you know that this happened once a day in specific time. After that Outlook users start to send again in email addresses of Contacts without problems and undeliver emails.

It's very easy but you must know about X500 Address to resolve this problem.

If you are interesting for Exchange Server or Office 365 you can find lot of courses from MVP and other Trainers in Pluralsight Console. 

To find more resources in our Blog  you can visit our Start Here page .

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I hope to find usefull my article. Do your comments here in Google+ or Facebook and i will be there to discuss with you.

Have a nice weekend and Holidays.