Mail error: 550 5.7.25 Client host rejected: cannot find your hostname, [107.191.109.199] (in reply to RCPT TO command)

[flameproof]

I have another issue that bugs me from time to time:

When using webmail from some receivers I get a bounce with:

550 5.7.25 Client host rejected: cannot find your hostname, [107.191.109.199] (in reply to RCPT TO command)

Server has 2 domains.

in Networking > Network Configuration

Hostname is (in virtualmin): vps.domain001.com

in Networking > Host Addresses

	127.0.0.1	Yes	localhost , localhost.localdomain
	::1	Yes	localhost , localhost.localdomain
	107.191.109.199	Yes	vps.domain001.com
	107.191.109.199	Yes	domain001.com
	107.191.109.199	Yes	domain002.com

Is there any obvious error?

Additional info: I use Cloudflare

SYSTEM INFORMATION
OS type and version	CentOS 6.10
Virtualmin version	6.08

[jimr1]

The only thing i can think of you are using centos 6 support for that died ages ago, you may find you get a better experience using an up to date os

[flameproof]

I am still on a 2Gb RAM VPS here. I plan to move to something more modern shortly.

[jimr1]

I have a 2gb ram with 2 processors … running Ubuntu 22.04 with no problems at all

[flameproof]

Yeah, but I am there like 10 years or so and I want to move to something cheaper and with more RAM. The VPS works, I don’t think it’s a good idea to work with an old systems you change in the near future anyway.