I have a web server that sends legitimate transactional email in high quantities. A reasonable percentage of users report that they never receive the emails. For every message sent, there's also a blind carbon copy going to an unfiltered email box on a different provider that I review to ensure the server actually sent the emails. All of the emails make it to my bcc box, so the server is sending the emails properly. It seems to be a spam filtering problem at other email providers.

The hosting provider for the web server indicates a reverse dns lookup has been set at their level linking the emails ip address properly to my server and domain.

Question: Is there anything else I can do to improve the rate that 3rd party service providers are filtering the emails I'm sending? Is there anything I can set on the DNS that I control to show that the server sending the emails is legitimate?