Outlook 2010 - Mail stuck in Outbox (Error 0x800CCC0B)


  • I'm having some issues with a client of mine, a school. Outlook 2010 has been installed for around a year, working away perfect using one of the staff email accounts. For some unknown reason a few weeks ago the account hasn't been able to send email, all email now gets stuck in the Outbox. When it gets stuck, I'm presented with the following error:

    Task ' - Sending' reported error (0x800CCC0B) : 'Unknown Error 0x800CCC0B'

    I have been through a range of different methods to figure this out (in no particular order..):
    - Uninstall/reinstall Office
    - Update Office to the latest service packs and hotfixes
    - Update the timeout period to 5mins (from 1min)
    - Remove/readd accounts, when I do this I can't actually reconfigure the account, when it attempts to do the test I get the following error:

    Send test e-mail message: The connection to the server was interrupted. If this problem
    continues, contact your server administrator or Internet service provider (ISP).

    Other information you may want:
    - The computer is joined to a domain, accessing the email remotely via POP3/SMTP
    - Receiving email works without any issues
    - The credentials are all correct and work on another computer next to this one
    - I have swapped the ethernet cable / port to the switch in case it was networking
    - The computer is running Windows 7 Professional x86
    - The computer is running Office 2010 Standard x86

    Any help/suggestions would be appreciated, I'm not opposed to thinking that it's an issue related to Windows instead of Office (and I've even seen references to it being a hardware issue, but this is a fairly new computer).

    Tuesday, April 30, 2013 10:18 AM

All replies

  • Have you tried to let another user log onto your computer and send a message to check if it would stuck in outbox folder.

    Per your description, the mail stuck issue would not happen when you acess your POP3 email account in another machine, sounds like there are something wrong on your own computer. Thus, we may try this:

    Method 1: Start Outlook in safe mode

    1. Type outlook.exe /safe in the Search box. 
    2.  Press Enter. 

    Starting Outlook in safe mode starts Outlook without add-ins, the preview pane, or toolbar customizations and could indicate a damaged profile or conflicting third-party application or add-in.

    Method 2: Create a new email profile

    Method 3: Delete suspicious messages from your mailbox

    If there is a damaged message in your mailbox, you can resolve this by doing one of the following:

    • Contact your ISP and ask them to delete any suspicious email messages. 
    • Delete any suspicious email messages by accessing your mailbox by using your ISP's web-based email program.

    Method 4: Disable your antivirus/firewall to check the result.

    Advanced steps, try to modify the regestry to check the result:

    1.  Quit Outlook. 
    2.  Click Start , and then click Run . 
    3.  In the Open box, type regedit , and then click OK . 
    4.  Locate, and then click to select the following registry key:
    5.  After you select the key that is specified in step 4, point to New on the Edit menu, and then click DWORD . 
    6.  Type UseInetcommCS , and then press ENTER. 
    7.  Right-click UseInetcommCS , and then click Modify . 
    8.  In the Value data box, type 1 , and then click OK . 
    9.  On the File menu, click Exit to quit Registry Editor.

    Feel free to post back.

    Tony Chen
    Forum Support
    Come back and mark the replies as answers if they help and unmark them if they provide no help.
    If you have any feedback on our support, please contact

    Wednesday, May 01, 2013 1:47 AM
  • Thanks for the reply, a lot of what you've suggested I have already tried though unfortunately (couldn't think of everything when I was writing it:

    I have logged on as another user, the same issues happen.

    I have ran Outlook in Safe Mode, again the same issues happen.

    I have actually manually disabled all Add-Ins to make sure this wasn't the issue, it didn't help at all.

    I have disabled antivirus (Symantec Endpoint Protection), I don't install it with Email Protection installed, but in any case it was disabled through all testing.

    I have cleared the webmail mailbox, so it doesn't seem to be an issue with a message inside of it - also given the error happens on testing sendmail at profile creation, it doesn't seem likely that could be the cause.

    I will test the Registry modification this afternoon and get back to you on that, hopefully this is the fix I have been looking for :)

    Wednesday, May 01, 2013 1:56 AM
  • Again, thanks for that Tony.

    Unfortunately I've given the Registry modification a try, restarted, it's still experiencing the same issue. Any other suggestions would be greatly appreciated :)

    Wednesday, May 01, 2013 3:43 AM
  • Hello Damian,
    Thank you for your update
    This is a quick note to let you know that we are performing research on this issue.

    Tony Chen
    Forum Support
    Come back and mark the replies as answers if they help and unmark them if they provide no help.
    If you have any feedback on our support, please contact

    Monday, May 06, 2013 2:26 AM
  • Hi,

    Since logging as different user gives the same issue , it is obvious that this is machine specific . We need to extensively troubleshoot the issue.

    Hence At this point of time I would suggest you to open phone support case with Microsoft. You can contact customer central on 1-800-936-4900 and create the case. Alternatively you can also visit to open case online

    Hope this helps

    Wednesday, May 08, 2013 3:15 AM
  • Just an update on this issue, I ended up reinstalling the operating system completely. I had Microsoft on the phone for a few hours attempting to solve the issue - they believed it was hardware related. I then had HP on the phone for hours attempting to solve the issue - they believed it was software related.

    In the end I gave up, I moved the computer to a part of the site that wouldn't require email and put another computer in it's place - unresolved, but now the environment works as it needs to.

    Monday, September 02, 2013 10:59 PM
  • Good afternoon Tony,
    Since last Thursday, August 10, 2017 – I have issue with 2 of our email accounts.
    Our MS Office is 2010 Pro Plus
    I can send email but when it’s starting receiving after a while I receive an error messages:
    1st – Task ‘operations @ shelbourneconstruction . com – Receiving’ reported error (0x8004210A):
    ‘The operation timed out waiting for a response from the receiving (POP) server. If you continue to receive this message, contact your server administrator or Internet service provider (ISP).’
    2nd – Task 'operations @ shelbourneconstruction . com - Sending' reported error (0x800CCC0B) : 'Unknown Error 0x800CCC0B'
    Here is what I did:
    1 – Removed account, scanned .pst and fixed the errors,
    2 – Created new account, imported email setting from fixed .pst,
    3 – Changed registry entry as you advised in your reply to the similar problem on the forum:
    In step 4.
    4 – In CMD I flushed DNS, Released IP and Renewed.
    5 – I called (Our domain provider) they re-synced our domain.
    Here is what happened after I finished.
    Operations email is working now, so I can send/receive emails, but accounting email is still having the same problem.
    Could you help me to find the solution for that problem, because it seems not working in all cases.
    Tuesday, August 15, 2017 4:58 PM