MAJOR ISSUE: Outlook stopped sending emails today and I am panicking!

Outlook 2010 has worked without issue for more than a decade. Today, I was trying to change my DNS service and the problem first occurred after I changed a few E-mail account settings and clicked ‘Test account settings’. This issue I am having is that when I try sending an email, I get: Task 'Pair of Docs Email - Sending' reported error (0x800CCC0F) : 'The connection to the server was interrupted. If this problem continues, contact your server administrator or Internet service provider (ISP).'

Based on what I read, I turned off the firewall, restarted Outlook, but same thing. Note that I do not have AV running on this machine, so that is not the issue. The problem is not the ISP since I was able to send email from another computer and I am still receiving email.

I ran scanpst on my outlook.pst file, but nothing was found. I also installed the demo version of Wondershare RepairIt and it claimed to have found something, but would not save the modified pst file unless I bought the program. Also, it started popping up a ton of browser windows that pointed to the same page, but they never appeared.

I then renamed the outlook.pst file and replaced it with a month-old backup copy, but I still had the exact same issue. I have checked the account stings and they all seem to be correct. I even rebooted the computer, but that didn’t help. I tried starting Outlook in safe mode, but got the same error. Some stuff talked about the ost file, but I am unable to locate such a file on my computer.

What on earth is going on????

I have done everything in that article, but no help. I also set the DNS records back to exactly as they were before I made the changes in Outlook. Still not working.

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I just installed another email program on this computer, copied the SMTP information from Outlook, and was able to send an email. This strongly suggests that the issue is with Outlook.

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I tried running 'repair' from setup.exe, but ran into a myriad of issues - all cannot locate file' such-and-such, even when i picked the directory the file was in. I then found the ISO file and reinstalled Outlook, but the issue persists. Maybe I have to uninstall then reinstall?

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Got it working again. The only thing that I can imagine was wrong was the capitalization of the SMTP user name...