After the setup of dns records for your domain in this guide you need to click on the button "Check dns records" to verify your domain authentification.
If the verification fails in the first time this means the dns requires some time to propagate ( up to 48 hours).
What should I do if my authentification fails?
Make sure that you added the dns records correctly as a TXT records
Wait few hours for dns propagation (up to 48 hours)
After few hours waiting go to account > sending emails and click on the button "Authenticate"
Click on "Check dns records" button. If verification is successful then close the popup and refresh your page.
If your dns fails after waiting over 48 hours and after verifying all steps above then contact our support.