Pop mail is sent using the smtp protocol. SMTP servers take your message and relay it, until it reaches the mail server of the recipient. Mail providers supply an smtp server for outgoing mail. However, with a home computer , most people send pop mail through their ISP's SMTP server. In fact, many ISPs will block attempts to use an external SMTP server.
If you have a mail account hosted by godaddy, they provide the option of sending mail through their SMTP server. To use it, the keeper of the godaddy account must enable your email address to use smtpout.secureserver.net by setting a quota. This is not enabled by default on the godaddy side,since most people are able to use their ISPs SMTP server to send godaddy mail.
Just to make things more complex: Some ISPs block use of external smtp servers by disabling the ports that they operate over. So if you are on wifi, you may have issues that you do not experience when using edge or 3g.
So: you can also try your ISPs SMTP server. There is also one from AT&T which will only work when you are on edge or 3g. I forgot the address but I will post it later.