How can I use cPanel hosting for Shopify email service?

[icmoptics]

I bought my domain when I created my Shopify page, so currently, everything is hosted & controlled by Shopify. 

I have a separate cPanel hosting at Hostinger where I host another webpage. If I were to use this cPanel hosting to serve emails for my Shopify webpage, what would be the best way to do it? 

I can add/change DNS records in Shopify, so this works perfectly and I can send/receive emails, BUT adding a DKIM record seems impossible: cPanel generates 2048 bit DKIM while, according to Shopify's support, "2048 bit isn't supported by Shopify."

They seem only to support 1024 bit DKIM. Any suggestion on how to solve this issue?