Question
We're a start-up based in California and have been sending out emails in blasts using Yet Another Mail Merge and MixMax. From what I can tell using the spam checking sites, we're in good shape, but our open and response rates have dramatically declined using the same templates for different contacts (which leads me to assume we're going to spam more).
Further - our clients are telling us that they missed some emails because our emails went to spam.
Answer
Here's an actual answer lol. Unfortunately you will probably have to purchase a tool like sendgrid, postmark, mailchimp etc. They keep their reputation high enough to help their clients' deliverability. It sounds like, though, you aren't certain deliverability is an issue, so it may also be a genuine drop in response. Has the email list changed? Has your frequency changed? These are all things to consider. Happy to do a call and try to help.