==== Required information ====
- iRedMail version (check /etc/iredmail-release): 0.9.5-1
- Linux/BSD distribution name and version: CentOS 7
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):  MySQL
- Web server (Apache or Nginx): Apache
- Manage mail accounts with iRedAdmin-Pro? Yes
- Related log if you're reporting an issue:
====

Hello,

I am trying to authenticate from an external VPS server to my iRedmail Pro server using SMTP to send out emails. I am able successfully authenticate (from an app running on the VPS) via SMTP to the iRemail server. The log on the app (running in VPS) even shows that it was able to sent out the email. However, I receive no emails on the other end. So, it appears the iRedmail either accepting those emails and not sending them out to the intended destination OR it is quietly dropping them.

Things I have done so far:
- Modified the /etc/postfix/main.cf file added the IP address of the VPS server to "mynetworks" and restarted postfix.
- Whitelisted the VPS IP within the iRedMail Pro
- Whitelisted the VPS IP within the IRedMail Pro for GreyListing
- Whitelisted the VPS IP in fail2ban and restarted it
- Modified the settings in the app (running in VPS) to use a different SMTP server and the destination emails arrive just fine. So, it is nothing to do with the app or the VPS server running the app.

Any idea what else I might be missing here?

Thanks.