Why is my mom having trouble sending SMTP emails with Thunderbird, but it works for me?

I just spent the past hour and a half doing Thunderbird tech support for my mom and my head hurts! I cannot for the life of me figure out why these email settings work for me and not her.

I created a GoDaddy email account for her rental property. We’ve followed GoDaddy’s Thunderbird instructions, as well as going with the automatic settings provided by Mozilla’s ISP database. My ISP is here in the U.S. and my mom uses an Italian one.

While setting up the account in TB, it took me mere seconds, just click-click-click and it worked. With her, nothing we have tried works and trust me, as far as I can tell, everything is set correctly. She also has a couple of Yahoo! Plus email accounts that I set up ages ago and which work just fine.

She can receive mail on this account, but she gets the following error messages when she tries sending:

“Sending of message failed. Please verify that your mail and newsgroups account settings are correct and try again.”

“Message could not be sent using SMTP server smtpout.secureserver.net for an unknown reason. Please verify that your SMTP server settings are correct.”

I find it really weird that I’m able to use the same exact settings (and my version of TB has one of her Yahoo accounts, as well, so the environment is almost the same) and she can’t.

Please help me.. I think my head is going to explode. :)