How to Load Balance SSL IMAP, POP3, and SMTP with HAProxy and Dovecot / Postfix

Load balancing encrypted email traffic (IMAPS on port 993, POP3S on port 995, and SMTPS on port 465) using HAProxy requires two critical mechanisms: SSL offloading at the load balancer and the PROXY protocol to preserve the client's real public IP address in Dovecot and Postfix logs.

Architecture: Encrypted Client → HAProxy (SSL Termination & send-proxy) → Dovecot / Postfix (Real IP Preserved)

1. HAProxy Configuration (haproxy.cfg)

frontend imaps_in
    bind *:993 ssl crt /etc/ssl/certs/mail.pem
    mode tcp
    default_backend dovecot_imaps

backend dovecot_imaps
    mode tcp
    server mail1 10.0.0.1:10143 send-proxy check

2. Dovecot PROXY Protocol Support (/etc/dovecot/dovecot.conf)

Configure Dovecot to accept the PROXY protocol header to log the real client IP:

service imap-login {
    inet_listener imap_haproxy {
        port = 10143
        haproxy = yes
    }
}
haproxy_trusted_networks = 10.0.0.0/24