How to fix e-mail that stops working in Windows XP?

Hi everyone!
I am a Windows XP user, and I am in trouble due to an issue with my e-mail. The issue is that my ISP e-mail is no longer working as far as receiving e-mails.
When I try to access my e-mail via my web browser, a strange message box appears containing the message “Error occurred with your POP3 e-mail server. E-mail server regioline not responded. ” Then I have no other choice than to click the "OK". This is really very strange issue for me because I am a victim of this for the first time. It's irritating as well because it has not yet fixed even after many attempts.
To solve this issue, first, I checked my account setting (thinking that there would be some problem), but even after changing my account settings into default, the issue still has not been fixed. I also have tried adding exception in my firewall, but there is no positive effect and I am still not able to send an e-mail.
Well, I have done my best to get rid of this strange issue, yet I failed to fix it and now I need some help from you.
I need to know How to fix e-mail that stop working in Windows XP?
Waiting.
Thanks
