It appears that this specific server is causing the problem. Here is the error message I'm receiving when trying to send an email:
Task Sending' reported error (0x800CCC6F) : 'Your outgoing (SMTP) email server has reported an internal error. If you continue to receive this message, contact your server administrator or Internet service provider (ISP). The server responded: 554 eastrmimpo109.cox.net cox too many bad commands from 72.196.246.44'
Cox should acknowledge that they have a problem and let us know the timeline for fixing it.