Some days back, I did added CDN on a shopify store and my Email forwarding stopped working.
Later, I got to know that Namecheap Email forwarding does not works with custom nameservers.
On further research, I found that free Email forwarding usually does not works with any registrar as soon as we start using Custom DNS and we need to purchase their Email hosting plans.
I found Improvmx.com and it did my job like charm. It is absolutely free service for Email forwarding, working like a charm with Cloudflare CDN.
Setting up is simple and hassle free and you will not be needed to pay a single penny.