In such situation TB should provide you with the reason why it can not deliver emails to our server. Did you receive any messages from it?
I suppose that the source of the issue is caused by incorrectly setup SMTP authentication in your TB. But it is only an assumption at this moment.
Anyway you also may submit a ticket at https://whbsupport.com and provide us with more confidential information (email login, IP, etc) which should help us to resolve your issue.
Thank you.
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Regards,
Eugene B.
Technical Support Team Shift Leader
WebHostingBuzz.com