I would like the text in the yellow block when setting a custom track-host be more clear. Currently it is all one block, but bullet points to point out the different CNAMES needed for HTTPS and HTTP would be great. Similar to the below:

To customize your track hostname, first you need to create a CNAME. In most environments, NAMEs are easy to create. Use a subdomain or host of your choosing (keep it short, ie: go, redir or r):
• User.mailiet.com. for HTTP links
• Uset.mailiet.com. for HTTPS links
The final dot may not be required by all DNS platforms, but it's syntactically incorrect.