Rebuild the Outlook for Mac 2011 database to resolve problems as recomended by Microsoft
Usually the maker (Microsoft) recommends the first thing to do is to REBUILD the database
That is a multiple step procedure and lengthy process so be ready for some work.
How to rebuild your identity database
Step 1: Quit all applications
You must quit all applications before you continue with the following steps. To quit an application, click the menu on the toolbar (top), and then select Quit. If you cannot quit an application or do not know how, hold down the Command and Option keys, and then press Esc on your keyboard. Select the application in the Force Quit Application window, and then select Force Quit. Click Force Quit to quit the application.
Note You cannot quit Finder.
When you are finished, click the red close button in the upper-left corner to close the window.
Fore Quit Applications window
Step 2: Determine the amount of space available on the hard disk
Before you perform any database maintenance, make sure that you have at least three times as much hard disk space available as the current size of your Outlook identity. For example, if the identity is 1 gigabyte (GB), there should be at least 3 GB of free space available on the hard disk (not including the space that is needed for virtual memory).
To determine the size of your identity, follow these steps:
n the Finder, click Go, and then click Home. Open the Documents folder.
Open the Microsoft User Data folder.
Open the Office 2011 Identities folder.
Click the Identity folder.
On the File menu, click Get Info, and then click Get Information. Note the size of the database.
When you create an Outlook identity, hard disk space is allocated for the data that the identity receives as you work. When you add and delete messages, appointments, tasks, and notes, the database can develop wasted space.
Step 3: Discover and back up the current identity
To back up your identity, follow these steps:
In the Finder, click Go, and then click Home. Open the Documents folder.
Open the Microsoft User Data folder.
Control-click or right-click the Office 2011 identities folder, and then select Duplicate. A copy of the folder is created.
Quit all applications.
You have created a backup of your identity (or identities) and are ready to continue.
Note This backup can be used by third-party database recovery software, which generally work better on non-rebuilt identities.
Step 4: Rebuild the database
Quit all applications.
Hold down the Option key on the keyboard, and then start Outlook 2011.
Note You can also browse to the Database Utility by opening the Application folder and then opening the Microsoft Office 2011 folder. Open the Office folder, and then double-click Microsoft Database Utility.app.
In the Database Utility window, select the database that you want to maintain, and then click Rebuild.
The Rebuilding Main Identify window will open and show the progress. When the operation is completed, you will receive the message "Your database was rebuilt successfully."
Click Done.
Select an identity
Start Outlook and see whether the problem is resolved. If the problem is not resolved, go to the next step.
Step 5: Create a new identity
If you are using Outlook in more than one capacity, such as at home and at work, Outlook may be configured to have multiple identities. Each identity stores separate sets of e-mail, address books, tasks, calendars, account settings, and more.
If Outlook has multiple identities, one of the identities might be damaged. Try to use a different identity to determine whether this is the problem. If an identity is damaged, you must create a new identity to resolve this problem.
To create a new identity, follow these steps:
Quit all applications.
Hold down the Option key on the keyboard, and then click the Outlook icon in the dock. The Microsoft Database Utility will open.
Note You can also access the Microsoft Database Utility by opening the Application folder and then opening the Microsoft Office 2011 folder. Open the Office folder, and then double-click Microsoft Database Utility.app.
Click the plus [+] sign to add a new identity, and then type a name for the new identity. For example, type New identity.
Create a new identity
Set the newly create identity as the default. To do this, select the newly created identity, click the Action button, and then select Set as Default.
Set an identity as the default
Quit the Microsoft Database Utility, and then restart Outlook and see whether the problem is resolved.
If the previous steps did not resolve the issue, the Outlook database most likely is damaged beyond repair. If there are no viable backups available and there are no other sources of the data (such as another computer or a handheld device), you will have to start from scratch because the data is not recoverable. To start from scratch, you have to drag the Office 2011 Identity folder (only if there are no other identities) to the Trash, and then restart Outlook.
Best Answer
Open the AppleScript Editor found in /Applications/Utilities. Paste in the following three lines:
Click the Run button at the top and this should delete every message in your Outbox.