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"Operation failed" error when sending mail via Outlook 2010

  • I just signed up for the beta and have added my Office 365 account to my email profile in Outlook. When I try to send or reply to email, I get "Operation Failed. The messaging interfaces have returned an unknown error. If the problem persists, restart Outlook. Cannot resolve recepient."

    This problem has been around in Outlook for a while, for example see the thread in

    In my case, here's what I find:

    - My profile includes one imap account, one Google Apps for Business email account (using the Google Outlook plugin), one Office 365 account

    - If I delete the outbound email user name in the To field and pick a contact from my contacts lists, I can send the email ok.

    - If I create a Profile with just the single Office 365 account it seems to work ok.

    Otherwise email works fine on all other clients (web, Windows Phone 7, Android Tab).

  • Hi Doug,

    It sounds like you setup a new profile for just the Office 365 account. After doing that did you attempt to add the IMAP and Google Business email account to it?  If not try that and see if all email works that way.

    If it still fails let us know and we can look further into the issue.  Please make sure all updates have been installed for your Outlook.  



  • Thanks for the reply. Yes, Office 365 on its own seems to work ok. When I add just the IMAP account, some addresses work and others fail after attempting to send. For example, I get the following error message (personal info replaced with xxxxx):

    Diagnostic information for administrators:

    Generating server:

    #550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##

    Original message headers:

    Received: from ([]) by ([]) with mapi id

    14.01.0225.042; Tue, 19 Apr 2011 05:37:44 +0000

    Content-Type: application/ms-tnef; name="winmail.dat"

    Content-Transfer-Encoding: binary

    From: Doug Miller <>

    To: "" <>

    So it looks like the send address is getting munged somehow.

    I don't have a way to add the Google stuff to an existing profile but I can add the Office 365 account info to a profile with just Google Apps. Similar failure issues.

    I have all the latest updates installed and installed the Office 365 client software.


  • Doug,

    This looks like an address auto-complete issue. In Outlook 2010 go to OPTIONS - MAIL.

    Under Send messages, click Empty Auto-Complete List.

    As far as the IMAP account; I suggest creating a brand new profile for it by going to Control Panel  / Mail

    I beleive that this should fix your issue.

    Thank You,

  • Thanks for the suggestion. It does appear to fix the problem and I can now receive and send mail from all three accounts in one profile.

    Thank you very much.


  • Well it looks like I jumped the gun. The issue is not resolved. Whenever I manually enter an email address in the To line e.g. and then try and send it I get a "The operation failed" popup. If the person is in my Contacts list I can click on To... and add them and it usually works. If it doesn't work, I can usually go to the addressee's properties and select the email type.

    However, if it is a new address there is no way to send mail from any of my accounts in the Profile. The address never resolves itself showing the underline and "Check Names" just brings up an error popup.

    I tried the Empty Auto-Complete List trick a few times but no luck.

  • I tried testing this with a standard Exchange account and found the same results - I could not send when I typed a new address into the To field.

    Tried digging on Google's site for help on this and have found out that it is not possible to have Google Apps and Exchange accounts setup in the same Outlook Profile. It appears to be a Google issue. For example, see here:

    Since I plan to use Office 365 as my central server for contacts and calendar, I have set up my Google account using IMAP instead of the Google Apps MAPI plugin. This seems to work fine however this will not help someone who needs to access both Google Calendar and Office 365 calendar from the same Outlook session.

  • Hi David,

    This is an old thread, but maybe reviving it will have some benefit. I have a client who is experiencing the 'Operation failed' issue when using the auto-complete feature with SOME addresses. He's using Outlook 2007 with Office365 and I backed up his PST prior to migrating to Office365 and restored it to the new profile. Clearing the Auto-complete list (found out how by searching) isn't really desireable as it's very convenient to just start typing a name and not having to go through the whole process of selecting an address from Contacts. I'm assuming that clearing the cache by renaming the nk2 file will wipe out ALL of the auto-complete entries and they will only reappear as individual addresses are invoked going forward. Is that true, and, if so, is there another way to resolve this issue at its root? What prevents Outlook from using these cached addresses in the first place? If its a bug, let's escalate the issue and get it patched.



  • I am experiencing the same issue.  office 365 integrated with google app sync in one profile.  Is there any solution?

  • In Outlook 2013, I too get the error "Operation Failed. The messaging interfaces have returned an unknown error. If the problem persists, restart Outlook. Cannot resolve recepient." I'm trying to use an Outlook profile created using Google Apps, to which I added my Microsoft Exchange Account.