Possible solutions, in order of how you should troubleshoot the problem.
1) Make sure your mail program is configured to login before sending email. This is usually called "My server requires authentication" or something similar. Make sure to check or enable that option.
2) Please disable your firewall and anti-virus then try sending your email again.
3) Check your Internet connection. If you are using wifi and a laptop, make sure you have enough signal strength and that you have eliminated the possibility for your connection to be disrupted. You may want to plug your laptop in directly to the Ethernet port on the router to see if it corrects the issue.
4) Restart your router.
5) Check the other available solutions located on the Microsoft Knowledge Base
6) Ask GlowHost support to check our firewalls to see if your IP has been banned. You will need to provide us with the IP address of the machine that is experiencing the problem. You can obtain the IP address from here:
Resellers, you can send your customers to another site if you like, so that they do not see the GlowHost brand name. Try whatismyip.com