Synchronisation error RRS feed

  • Question

  • Hi all,

    For a client we are doing an office 365 migration however I am getting sync errors on a mailbox whith the following user principle name: r&d

    This is mailbox is working in onprem but i am getting an error that:

    "The object failed to be synchronized because the attribute did not meet the validation requirements (format, character set etc.) of Azure AD. ""

    I think it has to do with the format character (&) but is there someway i can bypas this.

    It would be great if someone can help me.



    Friday, September 6, 2019 8:22 AM

All replies

  • I just run the idfix tool again and now i see the emailadres to fix it :-)

    However Idfix wants to update the value to rd instead of r&d

    So i have now asked the client how he or she logt in with that email adres because i dont know what the impact will be.

    Friday, September 6, 2019 9:14 AM
  • Hi,

    Thanks for visiting our forum, here we mainly focus on general issues about Outlook desktop client but your question is more related to Exchange online. So I'll move your thread to the dedicated forum for Exchange online.

    The reason why we recommend posting appropriately is you will get the most qualified pool of respondents, and other partners who read the forums regularly can either share their knowledge or learn from your interaction with us. Thanks for your understanding and hope your question will be resolved soon.


    Aidan Wang

    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact

    Monday, September 9, 2019 7:01 AM
  • Hi Jeffrey140,

    Ampersand (&) is an invalid character to be used in userPrincipalName and it will cause directory synchronization to fail - there is no way to by-pass it. Here are the general prerequisites regarding userPrincipalName:


    • The userPrincipalName attribute must be in the Internet-style sign-in format where the user name is followed by the at sign (@) and a domain name: for example, All Simple Mail Transport Protocol (SMTP) addresses should comply with email messaging standards.
    • The maximum number of characters for the userPrincipalName attribute is 113. A specific number of characters are permitted before and after the at sign (@), as follows:
    • Maximum number of characters for the username that is in front of the at sign (@): 64
    • Maximum number of characters for the domain name following the at sign (@): 48
    • Invalid characters: \ % & * + / = ? { } | < > ( ) ; : , [ ] " '
    • An umlaut is also an invalid character.
    • The @ character is required in each userPrincipalName value.
    • The @ character cannot be the first character in each userPrincipalName value.
    • The username cannot end with a period (.), an ampersand (&), a space, or an at sign (@).
    • The username cannot contain any spaces.
    • Routable domains must be used; for example, local or internal domains cannot be used.
    • Unicode is converted to underscore characters.
    • userPrincipalName cannot contain any duplicate values in the directory.

    Please visit the article linked below and check it out for a successful directory synchronization:

    Burak V.

    • Proposed as answer by Burak VAROL Tuesday, September 10, 2019 4:08 PM
    Monday, September 9, 2019 12:59 PM
  • Hi,


    I am writing here to confirm with you how the thing going now?


    If you need further help, please provide more detailed information, so that we can give more appropriate suggestions.



    Kelvin Deng

    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact

    Thursday, September 12, 2019 8:58 AM
  • Thanks we have removed the Ampersand (&) 
    Tuesday, November 19, 2019 1:46 PM