Referencing local AD instead of SMTP address
This article describes how to reference local AD instead of SMTP address.
1. In Office 365, create contacts for all on-premise users (email@example.com).
2. In on-premise AD, get the attribute LegacyExchangeDN for all on-premise users.
3. In Office 365, add the LegacyExchangeDN as X500 address to corresponding contacts.
How to implement these steps
1. To get the legacyExchangeDN attribute, go to on-premise Exchange Management Shell, run Get-Mailbox SOMEONE | FL legacyExchangeDN to get this attribute. For example, the LegacyExchangeDN we get is:
X500:/o=ABC/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=someone
2. Connect PowerShell to Exchange Online, steps is listed in the following article:
3. Create contact for USER in Exchange Online:
New-MailContact -Name “Some One” -ExternalEmailAddress firstname.lastname@example.org
4. Turn off address policy for this contact so Office 365 will NOT overwrite its email address automatically:
Set-MailContact -id “Some One” -EmailAddressPolicyEnabled:$false
5. Add the LegacyExchangeDN as X500 address to this contact:
Set-MailContact -id “Some One” -EmailAddresses “SMTP:email@example.com;X500:/o=ABC/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=someone”
6. Repeat the above steps for other on-premise mailboxes.
Note, if you have a large number of on-premise mailboxes, here is a script to help you to create contacts in batch
A sample script to perform the following steps in batch:
Copy the script to a file e.g., a.ps1
Ensure that the CSV files is created in the similar fashion (as per the sample csv file)
Place a.csv @ C:\ drive
This power-shell scrip will read the items\data from the Excel sheet
o Creates the mail contact with the ExternalEmailAddress (New-mailContact)
o Removes the EmailAddressPolicyEnabled:$false (set-mailcontact)
o Waits for few minutes for the Mail-contact to be created (sleep command)
o Reads the third column from the excel
o Converts them to the Array
o Sets the EmailAddresses on to the Object
write-host "Start of the Script!"
import-csv c:\a.csv | foreach
$obj=new-mailcontact -Name $_.displayName -ExternalEmailAddress $_.primary
$obj | set-mailcontact -EmailAddressPolicyEnabled:$false
write-host "Created the Object "$obj
write-host "Waited for a while for the object to be created!"
foreach ($x in $arr)
$obj.emailaddresses += $x
Set-MailContact -Identity $obj.Identity –EmailAddresses $obj.EmailAddresses -customAttribute1 "Migrated user"
write-host "done for this contact Object"
write-host "End of the Script!"
Sample Excel File (Saved as csv file):
smtp:firstname.lastname@example.org;SMTP:email@example.com;X500:/o=ABC/ou=First Administrative Group/cn=Recipients/cn=arvindsmirn
smtp:firstname.lastname@example.org;SMTP:email@example.com;X500:/o=ABC/ou=First Administrative Group/cn=Recipients/cn=cobrakingsa
smtp:firstname.lastname@example.org;SMTP:email@example.com;X500:/o=ABC/ou=First Administrative Group/cn=Recipients/cn=madarj
smtp:firstname.lastname@example.org;SMTP:email@example.com;X500:/o=ABC/ou=First Administrative Group/cn=Recipients/cn=madarjjaitra
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