I have downloaded a "turnkey"virtual machine containing a Zimbra installation.

I all went smooth and I am using Zimbra for the first time.
Although, after installation finished, I saw that there was a pre-configured domain "example.com" and a pre-configured server "mail.example.com".

I was able to add a domain "vpoffices.com.br" but I was not able to change the SMTP server to "mail2.vpoffices.com.br"

This is giving me a reverse DNS error on MXtoolbox saying that the Reverse DNS does not match SMTP Banner.

I think this could be the reason for not receiving any emails and not seeing any errors when sending.

Can someone please help me diagnose this problem?

Thank you,
Renato Rodrigues