We have been struggling with email issues on our network for some time now and need to find another option. We have a large network of domains that each send their own email via a custom PHP script(in real time). A lot of this email is falling out on the initial send because of various reasons that the receiving mail server doesn't like. Some email providers are worse than others at blocking our emails, such as AOL, but we see a lot of random fallout as well. Our email is in no way SPAM, just simple registration validations for the most part.
We have tried many different configurations, but from what I understand, our header footprint(which is custom) will never be widely accepted because of mail server SPAM filters that favor "common" footprints like gmail,yahoo,msn,hotmail,etc.
We send about 750 emails a day across our network from normal site usage such as registration confirmations, forgotten passwords, alerts, etc. We can't send a newsletter to our user base(100K) because it takes too long and the fallout is too high for it to be worth it.
Email is not our expertise and we are looking for solutions/ideas. Any thoughts/experiences with an outsourced solution? Is it worth trying to find someone to configure our server to keep it in house? What is everyone else doing?
I appreciate your feedback!