Spam rating (or spam score) is a mail server or filter’s calculated likelihood that a message is spam, based on dozens of signals evaluated together rather than any single factor.
Major factors
- Sender authentication (SPF/DKIM/DMARC pass or fail)
- Sender/domain reputation and send history
- Content signals (spam-trigger words, excessive links, poor text-to-image ratio, ALL CAPS subject lines)
- Recipient engagement (are your emails actually being opened, or ignored/deleted unread?)
- Complaint rate (recipients marking mail as spam)
Improving it
- Fix authentication first — it’s foundational and often the single biggest lever
- Keep complaint and bounce rates low by sending only to opted-in, actively engaged recipients
- Avoid purchased/rented email lists entirely — they reliably produce high complaint and bounce rates
FAQ
Does sending from a brand-new domain hurt deliverability?
Yes — a domain with no sending history has no reputation yet, which is why gradual volume "warm-up" is standard practice for new sending domains.