using SMTP for specific IP's not domain.com, SMTP information? postfix installed

hello everyone i have been using virtualmin since 2014 for hosting my website, it’s all good…
using
centos 7
postfix installed
recently, i thought about using few of my IP’s for mailing , and not using my main domain name IP so i want to use IP’s without using domain names…
the question is how i can use specific IP and what are the SMTP info for that IP ( SMTP like smtp.mydomain.com but i don’t want to use domain, username, password )?
and what are the things that i should consider installing for safe mailing?
also how can i know what are my SMTP info for my main domain? i mean usually smtp.mydomain.com or mail.mydomain.com, and ports, username, passwords ?
thank you

i know my questions sound stupid :slight_smile: i just don’t know how to explain
i know you have to make email on your server to use it as login to SMTP… i want to be able to use SMTP without making or entering email address that belong to a domain…

ok let me make it simpler in this link i can see if i want to use my hostname or my domain to send email from but i can’t see or i don’t know if i can put IP address in the place where it say (What domain to use in outbound mail )
https://doxfer.webmin.com/Webmin/Postfix_Mail_Server

this looks what i have searching for https://www.virtualmin.com/node/43462 but i can’t find the smtp_bind_address to change the IP

ok i just added the line smtp_bind_address = ip that i want to use, it should work i guess

it worked, i spent almost all day looking for solution, i think virtualmin should include this option in the panel to easy change the IP of sender

all good but this makes all my domains sends emails from the same IP, i want some domains to send from their own IP how i can do that

this fixed my problem https://docs.iredmail.org/send.out.email.from.specified.ip.addresses.html