Hello i just install IredMail on fresh server

I have 3 domains , i have create A record and mx record on my registrar for  mysite.com   , mysite2.com with same mx that mysite, mysite3.com etc

then i configure iredadmin for create other domains , and then i create user         user1@mysite2.com   user3@mysite3.com ect

When i log in roundcube i can send email to gmail, etc etc

But on gmail i want send email at user1@mysite2.com for example and i get error

Delivery to the following recipient failed permanently:

     user1@mysite2.com

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 554 554 5.7.1 <user1@mysite2.com>: Relay access denied (state 13).

So where is the problem ?

Thanks for your help