I wonder what are the best practices for resellers. Basically, I own a VPS with more than 70 websites. Each site has its own A records for the site and for the email (mail.domain.com). But the problem is that I only own 1 public IP address where everyone send emails from that particular IP address. Therefore, there is only 1 PTR record but multiple SPF and DKIM records. Now the problem is that some domains reject the emails from my customers due to the fact that PTR does not match with A record.
I know how to deal this with Microsoft Exchange but I have no idea how to do it with postfix. The idea I have in mind is to "route" all the emails from all the websites to mail.mycompany.com which has a PTR record. Unless you have a better idea.
Thanks in advance!