==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): latest
- Deployed with iRedMail Easy or the downloadable installer? download
- Linux/BSD distribution name and version: centos 7
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): Mariadb
- Web server (Apache or Nginx): nginx
- Manage mail accounts with iRedAdmin-Pro? yes
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

Hi,

I am getting complaints from customers that legit mail from o365 is being rejected.

One of the bounce messages contains the following:

Error Details
Reported error:  554 5.7.1 <NAM04-MW2-obe.outbound.protection.outlook.com>: Helo command rejected: Host not found
DSN generated by:        DM5PR1801MB1961.namprd18.prod.outlook.com
Remote server:   mail4.example.com

This is the 3rd time I have run into this problem.
Below are the 3 hosts involved:
NAM04-SN1-obe.outbound.protection.outlook.com
NAM04-BN8-obe.outbound.protection.outlook.com
NAM04-MW2-obe.outbound.protection.outlook.com

I have whitelisted the above but I am wondering if anyone else is seeing this?

I just checked again and NAM04-SN1-obe.outbound.protection.outlook.com now has an A record but the other 2 do not.

Is there a better way to handle this type of thing. I feel like this is going to be like playing whack-a-mole.

Regards,

Tom