If it says email.replies.m*s*g*s*n*d*r.com refused to connect:
That means you are using our HighLevel default Mailgun account. The links in our default Mailgun account won’t open.
To be able to open links in the emails, please use your own Mailgun Account or add an SMTP provider:
If it says email.mg.yourdomain.com refused to connect
That means the CNAME record might not set up properly.
1. To verify that, copy the bold part in the This site can't be reached page ---> email.mg.yourdomain.com
2. Go to MX toolbox to look up the Cname record:
3. If it says DNS records not found:
a. login to your domain provider
b. Go to DNS records and check the CNAME record
4. If it is already pointing to mailgun.org:
a. Go to Mailgun -> Sending on the left -> Domain Settings
b. Turn off Click Tracking
c. Send the email test again from HighLevel and you should be able to open the links in the email
5. If you want to keep Click Tracking on, you can email Mailgun support and they will let you know How to Enable HTTPS Tracking Links
If the info above does not help, please provide a screenshot to show all DNS records in your domain provider and send it to firstname.lastname@example.org