Debian UUCP Mail Cert Renewal

I run a Debian-based mail server that still moves messages over UUCP. The current security certificate has lapsed and I need it renewed and deployed so the system can resume encrypted connections without warnings. Right now I am not even sure whether the server expects an SSL, TLS or full CA bundle—so I will rely on your guidance to identify the exact requirement, generate or obtain the proper files, install them, and confirm that mail flow is once again secure.

Please document the steps you take so I can repeat the procedure next time or automate it with a short script or cron job.

Deliverables
• Verified, up-to-date certificate chain installed on the UUCP mail server
• Updated configuration files reloaded or services restarted so the change is active
• A concise README listing commands used, file locations, and any renewal automation (e.g., cron + certbot hooks)

Acceptance criteria: the server must pass an external certificate check without warnings, and mail clients must connect over encrypted channels without mismatch errors.