A Record changes automatically to old ip

My A record for mail is pointing to old IP.
So When I changes it to new IP, it automatically changes to old IP after one hour.

My email is not working. When some one sends email to me, they got following message -

Message not delivered

Your message couldn’t be delivered to {redacted}

Cloudflare doesn’t automatically change records. It is likely you have configured a 3rd party service/tool which is making the change. You should update/ configure that tool or disable it/modify your API key to prevent it from making the changes.