I use Zoho Mail and point my MX records to their servers. It worked fine at my old registrar (Google Domains) but when I point the nameservers to InfinityFree, the MX records don’t point to Zoho from the InfinityFree cPanel.
I think you use the control panel Cloudflare integration
so you have to read this
Are you using the control panel Cloudflare integration? A known issue of the control panel Cloudflare integration is that it breaks MX records (as well as custom CNAME records and subdomains). To receive email, you must disable Cloudflare on your domain name.
If you want full Cloudflare protection you best option is to move your domain to Cloudflare’s nameservers
and then there add MX and other record there.