There a number of services that rate messges likelihood of being spam and thus chucked into the recipient's junk mailbox. Google's spam algorithm for example has 200 rating factors
. The odds are it isn't your email address that is blacklisted, rather it is the content, format, and construction of your messages. There are services that will check the spam rating of your messages such as Mail-tester.com
. A google or DuckDuckGo search for "spam rating checker" will turn up many others. I suggest submitting some of your messages to one or more of these services and find out what your spam rating is.
Beause of spam rating factors, our church found it easier and more reliable to quit sending the newsletter in email and instead sends a notification message with a link to the actual content in a web page. Even with that, because of the number of messages we send we still have to use Constant Contact
to assure reliable delivery.