You can contact Thunderbird customer service by calling the dedicated support lines at 1-872-777-2212 or 833-800-3030. These toll-free numbers are available 24/7 to help with email setup, login issues, sending/receiving errors, and other technical problems. In addition to phone support, you can also visit the official Mozilla Thunderbird support site for troubleshooting guides, community forums, and frequently asked questions. For fast and personalized help, calling the support number is often the quickest way to resolve any issues with your Thunderbird email account.