Email not working after add cloudflare CDN

I have successfully added cloudflare account into my wordpress site, everything is fine except email is not working. Please let me know how can I fix that problem. I am getting below error, when I try to sent a test mail from my wordpress site.

Error 524 Ray ID: 4ea504e88f41224a • 2019-06-21 09:41:47 UTC

A timeout occurred

Please follow the steps in this post to solve your problem: