I have several domains where both websites and webmail work correctly, but email clients (e.g., Thunderbird, Outlook) fail to connect to the Postfix SMTP server due to an SSL error.
I am using Let’s Encrypt certificates, which I have manually renewed, but the issue persists, preventing secure email connections.
Error Log (Postfix mail.log)
"Feb 3 22:43:24 vmi2180301 postfix/smtps/smtpd[342347]: warning: Wrapper-mode request dropped from 51B6E287.dsl.pool.telekom.hu[81.182.xxx.xxx] for service smtps. TLS context initialization failed."
Troubleshooting Steps Taken
Checked that Let’s Encrypt certificates are valid and properly updated.
Confirmed that websites and webmail are working fine with SSL enabled.
Verified that Postfix is using /etc/postfix/vmail_ssl.map for SSL certificate mapping.
Ran postmap /etc/postfix/vmail_ssl.map and restarted Postfix, but the issue persists.
Checked file permissions and ownership for certificate files (privkey.pem and fullchain.pem).
Tested SMTP connection with OpenSSL, but it fails with write: errno=104.
I need help diagnosing why Postfix cannot load the Let’s Encrypt certificates properly despite being configured via vmail_ssl.map. How can I further debug this issue and ensure that email clients can connect securely?
