vBulletin forum :Problem with server Emails service ( not recieved) conflict with Cloudflare

I'm having an issue with my vBulletin forum; emails are not being received. I have already tried to troubleshoot the problem, but am not sure what may have caused the issue. I think it may be a conflict between my server and the Cloudflare service. I require assistance in understanding and resolving this issue as soon as possible.