frontend smtp_frontend
    bind *:25
    bind *:587            # **移除** ssl crt，讓後端自行處理 STARTTLS
    mode tcp
    default_backend smtp_backend

backend smtp_backend
    mode tcp
    server old_postfix 192.168.88.35:25 check

frontend imap_frontend
    bind *:993 ssl crt /etc/haproxy/certs/mail.pem
    mode tcp
    default_backend imap_backend

backend imap_backend
    mode tcp
    server old_dovecot 192.168.88.35:143

frontend pop3_frontend
    bind *:995 ssl crt /etc/haproxy/certs/mail.pem
    mode tcp
    default_backend pop3_backend

backend pop3_backend
    mode tcp
    server old_dovecot 192.168.88.35:110