qpsmtpd-forkserver[4357]: 4357 (connect) milter: milter Rspamd opening connection to milter backend
2981(rspamd_proxy) <05d697>; milter; rspamd_milter_process_command: MTA specifies too old protocol: 2, aborting connection
2981(rspamd_proxy) <05d697>; proxy; proxy_milter_error_handler: abnormally closing milter connection from: 127.0.0.1:43360, error: invalid protocol version: 2
Similar problem: https://www.b1gmail.eu/forum/thread/144-milter-version-%C3%A4ndern/
"rspamd cannot be forced to accept connections with version 2, even via lua script.
In https://github.com/rspamd/rspamd/blob/master/src/libserver/milter_internal.h#L156 it says that only version 6 is supported."