Exchange 2010: “You can’t send a message on behalf of this user unless you have permission to do so”

An user had “Send-As” permission on a shared mailbox. But user couldn’t send e-mail as “shared mailbox”.  User is doing it correctly (add the shared mailbox name in From field). But user gets this bounced message:

You can’t send a message on behalf of this user unless you have permission to do so. Please make sure you’re sending on behalf of the correct sender, or request the necessary permission. If the problem continues, please contact your helpdesk.

If user tries OWA to send the e-mail as the shared mailbox, it may work. If it is,  then it’s Outlook issue.

Solution: Have user update the offline address book (click Send/Receive tab, click Send/Receive groups and select Download Address Book). Better yet,

  1. Close Outlook
  2. Delete the offline address book folder under “C:\Users\username\AppData\Local\Microsoft\Outlook\Offline Address Books”  (I assume it’s Windows 7 computer, look under C:\documents and settings\username\…. for XP computers).
  3. Open Outlook and let it download new OAB.

Other Possibilities are,

  • You just gave “Send-As” permission for the user. Then, you have to wait for few hours. (you may restart Information Store to take effect the permission right away, who wants to do it? Smile)
  • User’s Outlook got bad/outdated cached contact information. Search for *.NK* files under user’s profile and delete it. Obviously Close the Outlook first before you delete the *.NK* files.

If it helped you, drop a reply to this blog.

63 thoughts on “Exchange 2010: “You can’t send a message on behalf of this user unless you have permission to do so”

      1. I add 2 users in distribution group, none of them cant send more of two mails on behalf.

  1. Getting this error when a user tries to update a recurring meeting. He gets this error for all attendees of the meeting. Any suggestions?

    1. You can try this,
      1. Genereate offline address book at the Exchagne server?
      2. Download new offline address book on the user’s Outlook after 10 minues.
      3. Try updating the recurring meeting again.

      You can also have the user try updating the recurring meeting using OWA.

  2. Life saver thank you very much. Microsoft may have his reasons not to facilitate Send As permissions management in the exchange information store but it is still annoying.

    This solves for me.

  3. This has been driving me round in circles for a week or two now. Hopefully your suggestions will sort it out. Seems wrong to me that all of the permissions are set on the server but the client is able to refer to a locally cached, obsolete “temporary” file and ignore what the server should dictate.
    I was hoping that all of the idiotic “OAB” issues from Exchange 2003 would have been fixed for Exchange 2010, obviously that’s too much to ask. What a shambles !

  4. This just saved me hours of troubleshooting, now I can actually test all the user accounts that I have to create through the day.

  5. Yep – I just needed to download OAB in the outlook clicent, didn’t need to delete the OAB files. Thanks for posting.

  6. Hi Anand, I’m having this same issue. Your suggestion to try and ‘send as’ from OWA worked for me, which is great progress. But after I closed Outlook, deleted my OAB files, restarted Outlook I still cannot ‘send as’ from Outlook. What else can I do??

    1. You can open Exchange Management Console and generate another offline address book. Then wait for 15 minutes, Open Outlook and try downloading the offline address book.

      I am guessing Server didn’t generate the offline address book with the changes you made (send as permission). So Outlook doesn’t know it’s has the permission.

  7. if you just added the send as options I recommend removing then reading the email address from the profile (in control panel>mail) it does it right away and you sound much better talking to your customer then just saying you have to wait a couple hours

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  9. Bullshit tried everything you suggested, dint worked waste of time…. we using outlook2010, our users getting same error massage when sending on-behalf

  10. One other thing you can try. If you have created a new e-mail domain you may have borked the end users ability to send-as. All permissions will be right. All the above solutions fail to fix the problem.

    Create a new mail as the user and remove the e-mail address from the ‘From’ drop down and then re-add it. It’s a fringe case, but that’s what resolved it for me.

  11. Had spent two days pounding my head against this. I had 3 users suddenly not able to send as, who had been sending as for years. Looking at it from both the server and permissions side and the client side. Today I ruled out the server, but still had no idea why the client wasn’t behaving. I had removed and rebuild the .pst and .ost files, and was nearly ready to wipe their profiles. I went in, saw two offline address books for each of the afflicted users… Deleted them, opened outlook and it worked perfectly. Thanks!

  12. Just an FYI.
    Had a similar issue when a user was trying to forward a contact card. Tried all the steps but nothing worked. It ended up being a corrupt contact card. Deleted it and recreated and it resolved the issue.

  13. I have been working on this for hours. Luckily after many searches I stumbled on this solution and it worked! Thank you so much.

  14. Deleting the offline address book worked for me as well! Office 2016 running on Windows 10 against Exchange 2010 SP3.

  15. For me, all above didn’t work but the following worked:
    1) Set Outlook in to online mode (uncheck “use Exchange-cached mode” in the outlook Profile)
    2) Close Outlook
    3) Delete all offline Cache C:\Users\\AppData\Local\Microsoft\Outlook\*.ost
    4) Start Outlook and put it back in Exchange-cached mode)

    This is to be used when the send as via OWA already works but does not want to work via Outlook.
    This has been tested with Outlook 2016 and Exchange 2010 as backend.

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