When newsletter performance declines, most people rewrite subject lines. Often the real issue is upstream: domain reputation, list hygiene, or authentication records nobody has checked in a year.
The checklist I run first
- SPF, DKIM, and DMARC configured and aligned
- Inactive subscribers suppressed or re-engaged, not just accumulated
- Send volume consistent week over week, not spiky
Why this matters more in 2026
Inbox providers have gotten more aggressive about reputation-based filtering, which means infrastructure neglect shows up as a content problem when it isn’t one.