Pepipost panel automatically validates the configured DNS changes in order to confirm your domain authentication process. However, it takes about 2 hrs to 24 hrs to sync the DNS changes globally configured on the DNS server of the sending domain.
You can wait for some more time and then click on “Validate DNS changes” option available under sending domains on your Pepipost account. In case if you still get the failure, you can connect with our Customer success executive on 24X7 live chat or write to us on support@pepipost.com