A user’s Office 365 email address unexpectedly contains an underscore character after directory synchronization

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Article ID: 2001616 - View products that this article applies to.

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After the Windows Azure Active Directory Sync Tool runs to sync your on-premises Active Directory environment to Windows Azure Active Directory, a user’s Office 365 email address unexpectedly contains an underscore character "_". 


This occurs if the user account in your on-premises environment has a proxyaddresses attribute or mail attribute that contains one or more of the following special characters:
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space character
(opening parenthesis
)closing parenthesis
@at sign
'single quotation mark
=equal sign
?question mark
/forward slash
In this scenario, after directory synchronization is run, the special character is replaced by an underscore character. Therefore, the user’s Office 365 email address contains an underscore character instead of the special character.


Remove the special characters from the proxyaddresses attribute of the user account in the on-premises environment.


The characters that are listed in the Cause section are treated as special characters in Office 365. Use of any of these characters may cause issues such as service disruption.

Still need help? Go to the Office 365 Community website.


Article ID: 2001616 - Last Review: September 11, 2013 - Revision: 12.0
Applies to
  • Microsoft Office 365 for enterprises (pre-upgrade)
  • Microsoft Office 365 for education  (pre-upgrade)
  • Microsoft Exchange Online
o365 o365a o365062011 pre-upgrade o365062013 after upgrade o365e o365m KB2001616

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