You may now add your custom tracking domain on Cloudflare.
Here are the steps to add them.
Log in to your Cloudflare.
On the navigation bar, click Select Website.
Select the domain and navigate to the DNS tab.
Click Add Record and enter the following details.
Type: CNAME
Name: inst
Content/Data: prox.itrackly.com
Double-check if the CNAME entry in Cloudflare is in DNS-only.
Go to Instantly and navigate Account Settings.
Click Add the new CNAME and add it as inst.yoursendingdomain.com in Instantly with your yoursendingdomain.com being the domain you added the CNAME record.
Click Check Status.
If everything is set up correctly, you will receive a notification below the Check Status: CNAME Verified SSL Verified.
Once you're done, click Save changes.