Pointing MX address to another server with cPanel without domain name

Lets say you have a client who have a website hosted with cPanel. But one day the client requests to point his mail exchange to their mail server. He only give you the IP address, without domain name.

Technically, you cannot point a MX address using only IP hostname, you must use a domain name. But in my case, I only have IP address. Here is how.

Using WHM, go to Edit DNS Zones menu. Choose your desired domain.

You will see a record :

sert.com.     14400     IN      MX     0     sert.com.
mail             14400     IN      CNAME sert.com.

Convert this record to :

sert.com.     14400     IN     MX     0      mail.sert.com.
mail             14400     IN     A     192.168.0.1

Change 192.168.0.1 with the IP the client give to you.

Click save settings, then try by yourself to ping mail.sert.com. If the mail.sert.com ping result still pointing to old IP address, clear your DNS cache. Here is how to clear DNS cache in all OSes.

If still not pointing to new, check your settings. Note all changes need max 48 hour to propagate to servers.