Email field problem

Can somebody help please.
The email field in CB does not take emails with .org for example jo@block.org
jo@block.com is ok , jo@block.co.uk is ok as well but not .org
I get this error message when entering jo@block.org:
//////
The server is temporarily unable to service your request due to maintenance downtime or capacity problems.
//////
My ISP says it not coming from the server, it is probably a configuration problem with CB.
Any idea, solution?
Many thanks.

Welcome to the forum.
Please provide some more information on your specific installation, e.g. Joomla and CB versions, additional Joomla or CB plugins you have installed. And if possible follow the Help Us Help You article in the FAQ

Does that mean that as soon as you enter the .org mail adress the site refreshes and gives you this error message? I've tried on my own server and the email check works as expected.

Thank you for your reply.
I have reinstalled CB and all is ok now. Probably a corrupted file.
Many thanks.

Glad it worked out and thanks for reporting your solution for future users who might encounter this specific problem