The secret about a successful export-to-pst and import-from-pst migration is called Add Custom Address, type X500

The last few months, I have had the below question pop up regularly…


is it possible to export the content of my On Premises mailboxes to PSTs, and then import them into my brand new Exchange Online environment?


Yes, you definitely export your mailbox content to a PST, and import that PST back into your new mailbox

But, the problem that usually pops up is, that when replying to a mail that has been imported back into the new mailbox from the PST, and it’s a reply to a another mailbox homed in the same mail environment, a user gets the following NDR:

Delivery has failed to these recipients or groups, The e-mail address you entered couldn’t be found…. as seen below:



One way of solving this, is when you reply to a mail imported from your PST, and destined for anyone in the same Exchange environment, to just remove the name, and search for it again in the Global Address List, that will work

But: is that user friendly?

Definitely not, so, time to investigate, and come up for a better way to solve this!

Setting the scene

I currently have an Exchange 2010 Sp1 On Premises deployed, with two mailbox-enabled users:


Both mailbox-enabled users have sent a few mails between one-another:


Now, I want to export the content of these two mailboxes to a PST, that I want to import into a brand new Exchange Online environment. First I will delegate myself (being the administrator) the abililty to export mailboxes to a PST using the Exchange Management Shell cmdlet New-MailboxExportRequest, by running the following line in the EMS: New-ManagementRoleAssignment –role “Mailbox Import Export” –user “MsBelgium\Administrator”


Followed by the export itself:, issuing New-MailboxExportRequest:


And double-check to make sure it’s finished, using Get-MailboxExportRequest:


Next up: Create two mailbox-enabled users in my Office 365 environment, and hand out the same e-mail addresses to both users:



Everything is looking as it should, being, ok Smile

Time to open up Robin’s mailbox using Outlook Anywhere, and import the previously exported PST file:




Everything seems to be in order, but now, Robin wants to reply to a mail received from his colleague Rita, now watch the MailTip provided by Outlook 20101


But let’s just ignore the warning provided by the MailTip, and press Send…. and let’s have a look at the NDR we are getting immediately:


and the below info, Diagnostic information for administrators:


Interesting, searching the web, got me more information about this issue, for example at the following links:

So, how to solve this?

Simple: Use the Exchange Management Shell, or the Exchange Management Console to add the X500 address to the mailbox-enabled users



After clicking OK, and checking with the Shell we can see the X500 address has been successfully added:


When replying to the same message, we don’t get the MailTip anymore Smile


And the message arrives, without any problem:


Exchange simply rocks!


Comments (11)

  1. Daniel Guretski says:

    I had the same issue with several users after migrating from Exchange 2003 to Exchange 2010 SP1.

    Thanks, great article!

  2. Anonymous says:

    Pingback from Migrating Exchange 2003 straight to Exchange 2013 | CodeTwo Squad Blog

  3. Anonymous says:

    Pingback from Migrating Exchange 2003 straight to Exchange 2013 | CodeTwo Squad Blog

  4. Anonymous says:

    Pingback from Migrating Exchange 2003 straight to Exchange 2013 | CodeTwo Squad Blog

  5. Anonymous says:

    Pingback from Migrating Exchange 2003 straight to Exchange 2013 | CodeTwo Squad Blog

  6. Anonymous says:

    Pingback from Migrating Exchange 2003 straight to Exchange 2013 | CodeTwo Squad Blog

  7. Ahmed Atia says:

    I had the same issue after exporting Exchange 2010 SP1 mailboxes to PST, then importing them to new Exchange 2013 SP1 in a new Active Directory forest.

    Didn’t think I would find a solution for that. I instructed the users to remove the mail address and select it again from the address book, as you mentioned in the first solution.

    Having read this article, I’m going to try your second solution, since it would be more convenient to the end users.

    Thanks in advance!

  8. james says:

    Excellent article – works for me. Many thanks

  9. Lee K says:

    Would this apply to a migration from 2003 to 2013 exporting the .PST and then importing

  10. show box says:

    Thanks for the great info. I really loved this. I would like to apprentice at the same time as you amend your web site, how could i subscribe for a blog site?
    For more info on showbox please refer below sites:
    Latest version of Showbox App download for all android smart phones and tablets. – It’s just 2 MB file you can easily get it on your android device without much trouble. Showbox app was well designed application for android to watch movies and TV shows, Cartoons and many more such things on your smartphone.
    For showbox on iOS (iPhone/iPad), please read below articles:
    Showbox for PC articles:
    There are countless for PC clients as it is essentially easy to understand, simple to introduce, gives continuous administration, effectively reasonable. it is accessible at completely free of expense i.e., there will be no establishment charges and after establishment
    it doesn’t charge cash for watching films and recordings. Not simply watching, it likewise offers alternative to download recordings and motion pictures. The accompanying are the strides that are to be taken after to introduce Showbox application on Android. The above
    all else thing to be done is, go to the Security Settings on your Android telephone, Scroll down and tap on ‘Obscure sources’.
    Movie Box, an esteemed movies application in which you can find stacks of programs and films. The guide is given here to download Movie Box app to Android and to Apple iOS 9.0.2, iOS 8.4/8.3 and also for the lower versions without Jailbreak.
    Please do login to Showbox application with the help of Ymail. You can login in Ymail from here –
    Sign Up & Do registration for latest movies on Showbox application

  11. Peter says:


    But THIS doesnt work in OFFICE365 so WHY would M$ consultants send me HERE???

Skip to main content