If you have already read https://help.docsify.net/514463-How-to-set-up-a-custom-domain-for-tracking-emails-and-links and been setup your custom domain for email and link tracking you want to check whether it ’s working for your emails, do the next steps:
Write an email and add a link there
To test email and link tracking, you should follow this steps https://help.docsify.net/880009-How-to-test-Docsify-by-your-own
Open the email and tap on the link and it should show you where the link leads.
If it’s your custom domain, that means that you made everything correctly.