windows 7 and outlook 2010 microsoft security username and password request

Stephens answer is closer, but I can't believe how many people were so off the mark with their responses.

Basically, Outlook 2010 on Windows 7. The default account is the mailbox on the corporate Exchange Server.

Every time Outlook is started, it pops up a Windows Security login prompt. Nothing to do with malware. This is "by design", but only in certain circumstances, such as "always prompt for credentials" being checked.

Another is that you have Outlook logins defined in the Credential Manager.

Close Outlook, goto Start>Control Panel>User Accounts, click "Manage your credentials", scroll down to "Generic Credentials" and remove from the vault any that start with "MS.Outlook:".

Now when you start Outlook it'll use your corporate domain login without prompting.

This situation occurs if you add multiple accounts to Outlook that have different logins, and then remove some of those accounts. The stored credentials get left behind and Outlook can't decide which one to use.

I am moving your thread to the Outlook forums as I believe that this is an Outlook issue. You could check in your account settings in Outlook - more settings/security tab to see if the "always prompt for credentials" option is checked.

-steve