I enabled smtp_tls_connection_reuse in Postfix main.cf and saw “Cannot start TLS: handshake failure” for new emails being generated and mail flow stopped.
I later figured out based on the doc that smtp_tls_connection_reuse has dependency on tlsproxy process and that wasn’t enabled in master.cf
- Uncommented tlsproxy line in /etc/postfix/master.cf file.
- Restarted postfix service
systemctl restart postfix
- Now email flow started working.
Thanks you for reading !