Different A Addresses for Main Domain and Email

So this maybe a long shot!

However, I have client and there structure for hosting is:

Hosted under my VPS server:

• Main Domain: Pointed to Wix
• Email Domain: Pointed to my server
• Subdomain(s): Pointed to my server and running different scripts/redirecting to other URLs

The subdomains are working fine under my hosting however, the emails aren't working. I was wondering is there away to have two different A addresses or different IPs for Main Domain and Emails?

As of right now I have:

• DOMAIN.COM - A - WIX IP
• www - CNAME - WIX NAME
• mail - CNAME - DOMAIN.COM

Then when I tried to do:

• mail - A - VPS IP

I got an error stating that I couldn't do so as I already have a CNAME.

Can anyone help me?!

Make it:
DOMAIN.COM - MX - mail [MX records list DNS names with A/AAAA records]
mail - A - VPS IP

It should allow you handle messages for user@domain.com by accepting incoming SMTP sessions/connections at VPS IP.