SpamAssassin is available on the Business tier.
Parcel integrates SpamAssassin so you can easily check if your email is likely to be caught in spam filters. Check your email's spam score by clicking the SpamAssassin button in the bottom right corner. You can re-run the SpamAssassin check at any time by pressing the Refresh button. The lower the score, the better. Higher scores are more likely to be sent to Spam.
Learn more about the SpamAssassin score and tricks.