I am trying to send out my monthly newsletter to clients and they are being marked as spam.

No one is getting them as they are being filtered and/or moved to their junk mail box.

Answer:
You can't control the recipients server if it considers your emails as spam, you can look on the Internet to read information on why servers consider your emails as spam. Sending large amounts of mail with the same content will look like spam

You will need to use email broadcast software to avoid this. We offer a comprehensive email marketing service or software option. Please go to our product information sheet