Ошибка сертификата при прямой доставке электронной почты

[JammyDodger]

Это может помочь?

Self-hosted mail-receiver update following Let's Encrypt root certificate change

This announcement only affects self-hosters who are running Configure direct-delivery incoming email for self-hosted sites with Mail-Receiver. Managed hosting customers, and self-hosters using POP3 for incoming mail are not affected. As you may be aware, Let’s Encrypt recently changed their root certificate. The old root certificate expired today, and has caused a number of issues for out-of-date clients across the web. All of our systems at CDCK are up-to-date, and were not affected by today’s…

Не знаю, как давно у вас отключена входящая почта, но, возможно, пересборка mail-receiver в любом случае поможет?