# Developer troubleshooting guides

Work through SPF lookup limits, DMARC enforcement, DKIM key failures and JWT verification with practical steps, tool links and explicit limits.

Canonical: https://tamperbox.dev/guides

Updated: 2026-10-18

Reviewed: 2026-10-17

Start with the failure you can observe, check the underlying evidence, then verify a change before relying on it. These guides link to tools that show their processing boundaries and limitations.

## Guides

- [Fix SPF PermError: too many DNS lookups](https://tamperbox.dev/guides/fix-spf-too-many-dns-lookups)
- [DMARC rollout: from p=none to reject](https://tamperbox.dev/guides/dmarc-monitoring-to-reject)
- [Why is my DKIM key failing?](https://tamperbox.dev/guides/fix-dkim-key-failures)
- [How to decode and verify a JWT safely](https://tamperbox.dev/guides/decode-verify-jwt-safely)