If your server is behind a strict firewall, whitelist the MailWizz license server IPs (contact support for the current list). Also whitelist port 443 (HTTPS).
MailWizz is self-hosted software. The license key does not "unlock" features; it primarily enables automatic updates and verifies your installation as legitimate. mailwizz license key work
Your license key is registered to mailer.yourcompany.com , but you’re trying to run MailWizz on newsletter.yourcompany.net or on a temporary IP address. If your server is behind a strict firewall,