I would suggest changing your email address on file to a Gmail or other email address as this seems to be local to your email provide, I'm afraid. We typically do not have any issues emailing other clients.
Unfortunately, I would advise contacting your hosting provider for assistance here as there will need to be an error for us to escalate the ticket. The error you're getting is a lot like that of your car's check engine light, it says there is an issue but not exactly what or where. We need that what or where to proceed troubleshooting.