The company aaa.com send the email to a company ccc.com which share email
server with a company bbb.com.
Before it was not the problem at all, all the email were went through fine,
until the company bbb.com implemented a reverse look on the SMTP connector to
prevent spam.
Now the funny thing that when a company aaa.com can send email to a company
bbb.com but not a company ccc.com.
This happen not for all domains only some domains?

A company bbb.com and a company ccc.com share the mailserver.

Is anyone had this issues or experiencing with this kind of problem?

Any help will be appreciated!
Ott