If you are having issues with outlooking giving error 0x800cce05  and sending emails expecually in windows 10 this is due to system files being corrupt, I had this issue on a brand new Acer laptop

To resolve the issue follow the below

Run the System File Checker tool (SFC.exe)

To do this, follow these steps:

  1. Open an elevated command prompt. To do this, do the following as your appropriate:
    Right click the start button and select “Command Prompt (Admin)”
    Windows 10, Windows 7, or Windows Vista

    To do this, click Start, type Command Prompt or cmd in the Search box, right-click Command Prompt, and then click Run as administrator. If you are prompted for an administrator password or for a confirmation, type the password, or click Allow.
    A screenshot for this step.
  2. At the command prompt, type the following command, and then press ENTER:
    sfc /scannow

    A screenshot for this step.

    The sfc /scannow command will scan all protected system files, and replace corrupted files with a cached copy that is located in a compressed folder at %WinDir%\System32\dllcache.
    The %WinDir% placeholder represents the Windows operating system folder. For example, C:\Windows.

    Note Do not close this Command Prompt window until the verification is 100% complete. The scan results will be shown after this process is finished.

  3. After the process is finished, you may receive one of the following messages:
    • Windows Resource Protection did not find any integrity violations.

      This means that you do not have any missing or corrupted system files.

    • Windows Resource Protection could not perform the requested operation.

      To resolve this problem, perform the System File Checker scan in safe mode, and make sure that the PendingDeletes and PendingRenames folders exist under %WinDir%\WinSxS\Temp.

    • Windows Resource Protection found corrupt files and successfully repaired them. Details are included in the CBS.Log%WinDir%\Logs\CBS\CBS.log.

Now reboot your computer and you should be able to send mail! you might have to delete existing outbox mail and create a new email to send.