1. LDAP attributes using iredadmin - pro ?
Check the tutorial:
https://docs.iredmail.org/per-account.transport.html
which is the server to received email, and mail2 mail3 mail4 users send mail to outside is thru mail1, my question is how do i do that?
FYI: https://docs.iredmail.org/relayhost.html
using iredadmin i create all the users in our domain, and configure relay on user that is not on the sites to the server it belong, it worked! but i don't know if it is the correct way.
Yes, under the "Relay" tab in user profile page.