The certificat authority that issued your client's certificate is unknown to postfix.
- Add the CA to /var/spool/postfix/etc/ssl/certs/ - Add to the global /var/spool/postfix/etc/ssl/certs/ca-certificates.crt file Add these two lines to your main.cf smtp_tls_CApath = /etc/ssl/certs/smtp_tls_loglevel = 1 The CA's certificate and the intermediate certificate should also be part of your client's certificate too. See if that helps. From: rei <reinl...@gmail.com> To: postfix-users@postfix.org Sent: Monday, September 5, 2016 11:25 AM Subject: SSL3 alert read:fatal:unknown CA I keep getting these errors when trying to send email using TLS connection: SSL3 alert read:fatal:unknown CA SSL_accept:failed in SSLv3 read client certificate A SSL_accept error from xxx.com[159.203.103.107]: 0 warning: TLS library problem: 6605:error:14094418:SSL routines:SSL3_READ_BYTES:tlsv1 alert unknown ca:s3_pkt.c:1259:SSL alert number 48: The certificate is self-signed (generated using OpenSSL) and it has been added to Postfix configuration: smtpd_tls_cert_file = /etc/pki/tls/certs/server.pem smtpd_tls_key_file = $smtpd_tls_cert_file What caused those errors? How to fix them? -- View this message in context: http://postfix.1071664.n5.nabble.com/SSL3-alert-read-fatal-unknown-CA-tp85984.html Sent from the Postfix Users mailing list archive at Nabble.com.