I have an issue with a small percentage of emails going out from our Exchange 2000 / SBS Server.
These are being bounced back with 554 5.7.1 <xx-xx-xx-xx.dsl.pipex.com[xx.xx.xx.xx]>: Client host rejected: Access is not allowed>
(I obscured the ip address).
From research it seems that we do not have a valid Reverse DNS entry as this seems to point to our ISP Pipex and not to our domain name.
Am I right in thinking that some mailservers require the reverse DNS entry to match the sending domain name?
I have spoken to Pipex and they refused to set up Reverse DNS for us! So apparently the only option is to forward all mail through their SMTP server.
Is this correct ? If so, what are the implications of this and the fact that we don't have a valid reverse DNS at our company?