==== Required information ====
- iRedMail version (check /etc/iredmail-release): latest
- Linux/BSD distribution name and version:  debian
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): ldap
- Web server (Apache or Nginx):
- Manage mail accounts with iRedAdmin-Pro?
- Related log if you're reporting an issue:
====

goal: ability for user receive and send email from other address from other domain. i don't want to remove restriction reject_sender_login_mismatch and give all users to send email from every account. I just want to give one user to send email as other user form other domain. Both domain is on same server.

Example.
exist user: user1@first.com
mail to receive and send:  user2@second.com

It's not possible to make alias from iredwebinterface to other domain , but it's possible to make it directly in ldap.
I added field shadowsAddress: user2@second.com to user1@first.com, now user1@first.com  able to send email as user2@second.com. But then i try to send mail from external server to user2@second.com , postfix answer that relay access deny. And i cannot add user2@second.com as user , because webinterface write me , that user already exist.

Why i get  "relay access deny" to shadowadress?  How can i solve problem?