==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version: 1.6
- downloadable installer
- Linux/BSD distribution name and version: debian 11.4
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP
- Web server (Apache or Nginx): nginx
- Manage mail accounts with iRedAdmin-Pro? no
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

The names of my local (domain_local) and mail (domain.com) are different from each other. Set up user authorization according to the instructions:

https://docs.iredmail.org/active.directory.html

I also saw this thread: https://forum.iredmail.org/topic3165-in … omain.html

As a result, it turns out that a user with login username@DOMAIN_LOCAL (in upper case), not username@domain.com, can log in to roundCube, and through a mail client. But when I try to send a letter to any address, I get the message "<username@domain.com>: Sender address rejected: User unknown". What's wrong, how to fix it?