==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release):  0.9.7 MYSQL edition
- Deployed with iRedMail Easy or the downloadable installer? downloadable installer
- Linux/BSD distribution name and version: ubuntu 16.04
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Apache
- Manage mail accounts with iRedAdmin-Pro? no
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

Hi,

Currently my company using GMAIL for mail server, our old staffs are already have account on gmail:
1. staff1@company.com
2. staff2@company.com

then we need to setup our mail server, i've installed iRedMail on this new server and already running. I've created new email account on this server:
1. staff3@company.com
2. staff4@company.com

our mx record point to gmail server, and on gmail i've set a rule to catch unrecognized address to my new server.

sending and receiving email from another domain are fine. But problem happen when account on new server try to send email to address on gmail server.
it always got same error 'Undelivered Mail Returned to Sender   : user unknown'

my configuration changes on postfix:

#check_policy_service inet:127.0.0.1:7777
local_recipient_maps =
virtual_mailbox_maps =
#    proxy:mysql:/etc/postfix/mysql/virtual_mailbox_maps.cf
transport_maps =
#    proxy:mysql:/etc/postfix/mysql/transport_maps_user.cf
#    proxy:mysql:/etc/postfix/mysql/transport_maps_domain.cf

regards,
Bintang