New install AlmaLinux 8, aaPanel 6.8.36 with only mail server 4.7 installed, there is no webserver
openssl s_client -connect mail.domain.com:587 -starttls smtp returns error
Start Time: 1711355244
Timeout : 7200 (sec)
Verify return code: 21 (unable to verify the first certificate)
Extended master secret: no
Max Early Data: 0
I tried solutions from related posts - smtpd_tls_chain_files in config are correct, reapply certificate and restart services also not helps.
Port 25 is still not open - that should not affects the certificate check.