==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): iRedMail-1.5.2
- Deployed with iRedMail Easy or the downloadable installer? 1.5.2.tar.gz
- Linux/BSD distribution name and version: Alma8
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro?
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

Hi,
I am trying to follow this guide https://docs . iredmail . org/relayhost . html

And it says to use user and password

Then write the username and password in /etc/postfix/sasl_password:

relay.server user:password

But where do we get the user and password?

The error I am getting in roundcube is this

Reporting-MTA: dns; mail.domainname . com
X-Postfix-Queue-ID: 4L3QG44p8yzB7Hcj
X-Postfix-Sender: rfc822; postmaster@domainname . com
Arrival-Date: Wed, 18 May 2022 16:54:20 -0400 (EDT)

Final-Recipient: rfc822; gmail@gmail . com
Original-Recipient: rfc822;gmail@gmail . com
Action: failed
Status: 5.7.1
Remote-MTA: dns; lon-tls.heficed . com
Diagnostic-Code: smtp; 550 5.7.1 Authentication required

And I dont know how to do Authentication

Thanks