Mail can land in spam for many reasons, including weak domain authentication, poor message reputation, suspicious content, broken DNS, or recipient-side filtering rules. There is rarely a single universal cause.
- Confirm SPF, DKIM, and DMARC are set up correctly.
- Use consistent sender identity and domain alignment.
- Avoid spam-like content, deceptive subject lines, and risky link patterns.
- Make sure your domain and sending behavior have a clean reputation.
- Test with multiple recipient providers when troubleshooting.
If delivery is inconsistent, start by checking authentication and DNS first. Those are among the most common causes.