Messenger:consume email is very slow

I use this

Have a full guide but is outdated. Will try to update it this week.

This post answer solves my need specifically via SES.
Only 1 worker running, not many simultaneously.

BTW, I configured both servers to be able to use SES as the SMTP directly from EXIM or POSTFIX instead of included SMTP server (2 servers, 1 with postfix, other with exim).