==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release):  Iredmail 1.71
- Deployed with iRedMail Easy or the downloadable installer? Downloadable installer
- Linux/BSD distribution name and version: Ubuntu 24.04
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP
- Web server (Apache or Nginx):
- Manage mail accounts with iRedAdmin-Pro? Yes
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

Hello, everyone!

I’m new to iRedMail. I’ve set it up correctly, and I’m able to send and receive both internal and external emails without any errors.

I’m using Microsoft Active Directory for user authentication.

However, my problem arises when a user has two email accounts under a single Active Directory account. I can’t log in to the second email account.

iRedMail is authenticating only against the default UPN for the user object and not against the alternate UPNs.
For example:
user@primary.com (the default AD UPN) can log in, but user@secondary.com (an alternate UPN) cannot.

Has anyone encountered this issue before?