With the account type you have and the email editor you are using there is not a Spam Check button available for you. I would suggest making sure you're not including anything that makes your email look like spam (All caps in the subject, excessive punctuation, words like "Earn money!", etc). Here's a list to get you started.
Another suggestion- Before you send, share your campaign in our Critique my Campaign board so other users can give you some feedback! Someone else might catch something you missed.