受信メールサーバーに証明書エラーがあります

[Simon_Manning]

If it started last November, that’s almost certainly the Let’s Encrypt root certificate expiry. You should just need to pull the new image and rebuild.

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

This announcement only affects self-hosters who are running Direct-delivery incoming email for self-hosted sites. 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 The old root certificate expired today, and has caused a number of issues for out-of-date clients across the web.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 expiration. Unfortunately we…