Outlook is one of Microsoft's most frequently updated programs, due in no small part to the updates that must constantly be released for the Outlook junk mail filter to combat spammers. If your copy of Outlook is not kept up to date, it may contain security vulnerabilities and most likely does not contain the most recent junk mail filters released by Microsoft. Update Microsoft Outlook to resolve these issues.
Windows Vista and 7
Click the "Start" button, and type "Update" into the search box at the bottom of the Start menu. "Windows Update" should appear. Click it to launch the Windows Update utility.
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Click the "Change settings" link.
Put a check in the box under "Microsoft Update" and click "OK." This tells the Windows Update utility to check for updates for all of the Microsoft products installed on the computer, rather than just for Windows itself.
Click "Check for updates." A list of available updates for your computer will be shown.
Click "Install Updates" to install all available updates. You may need to restart your computer after this process is complete.
Open Internet Explorer and browse to windowsupdate.Microsoft.com.
Click the "Express" button to download the most important updates for your computer. These updates will include anything available for your Windows installation, and updates for Outlook and the rest of Microsoft Office.
Click the green "Install Updates" link to install all available updates. You may need to restart your computer after this process is complete.