BleepingComputer.com: Outlook 2007 - Cannot Send Emails

Hello,

The computer's OS is Windows Vista and the version of Outlook is Outlook 2007.

I have noticed that the e-mails sent through Outlook 2007 aren't going through. Upon sending them, they remain in the Outbox and are labeled "This message has not been sent." Sending them again from the Outbox does not change this, and I have no idea how long this has been going on. I have looked under the account settings in Outlook and used the program's Test Account Setting feature to identify an error message. The account will log into the incoming mail server (POP3) just fine. It cannot send a test e-mail, however, and will display this error message after failing:

Quote

What can I do to make Outlook work again?

Steps I have taken so far:

- I have tried the How to Troubleshoot Outlook when you cannot send or receive e-mail solutions, as provided by Microsoft Support. It suggested 1) making a new profile and sending a test e-mail to myself, which did not work, and 2) verifying that my connection used TCP/IP, which it does. This too did not solve my problem.

- I have also seen solutions that require altering the outgoing server settings, particularly the "My Outgoing Server (SMTP) requires authentication" checkbox. I have seen solutions that involve checking or alternatively, unchecking this box. Doing either does not allow me to send an e-mail. Currently, I have that box checked (as it always had been).

- Additionally, I've read that this computer's antivirus, McAfee, may interfere with the sending of e-mail thanks to the antivirus's email scanner. Following the suggestion, I disabled that part of McAfee but still was unable to send an e-mail. Currently, I have McAfee's e-mail scanner back on.

I think I have gone as far as I can on my own! It's the computer of a family member, and I'm only marginally more savvy at this sort of thing than she is; I'd appreciate it if you could simplify any solutions for my sake.