Tom Harris
Infrastructure Reviewer, Puzzle Inbox
Tom focuses on DNS, authentication, and bulk-sender compliance. He has spent eight years inside cold email agencies running infrastructure for 25+ clients per cycle.
Tom has spent eight years building and breaking cold email infrastructure inside agencies. His writing on Puzzle Inbox focuses on the parts of outbound nobody likes to think about: DNS configuration, bulk sender compliance under Google's and Yahoo's 2024 rules, blacklist recovery playbooks, domain rotation strategy, and the per-platform anti-abuse policies that quietly throttle cold email volume. He tests every blacklist, every SPF lookup tool, and every DMARC monitoring service that gets named in the blog.
Areas of expertise
- Cold email DNS setup
- SPF DKIM DMARC
- Google bulk sender requirements
- Microsoft 365 anti-abuse
- Blacklist recovery
- Domain rotation strategy
Recent articles by Tom
- Cold Email Deliverability Audit: The 14-Point Checklist — Jan 18, 2026 · 11 min read
- The Best Time to Send Cold Emails (Based on 2M+ Sends) — Mar 6, 2026 · 10 min read
- Cold Email Follow-Up: The Complete Guide to Not Being Annoying — Mar 4, 2026 · 12 min read
- B2B Lead Generation in 2026: What Actually Works (And What Is a Waste of Money) — Feb 25, 2026 · 15 min read
- Cold Email vs LinkedIn Outreach: Which Actually Works Better? — Mar 18, 2026 · 12 min read
- Cold Email for Recruiting — What Works Differently — Mar 19, 2026 · 13 min read
- How to Keep Your Cold Email Bounce Rate Under 2% — Mar 25, 2026 · 7 min read
- Cold Email Reply Rate Benchmarks by Industry — 2026 Data — Mar 25, 2026 · 8 min read
- How to Build a Cold Email Prospect List That Converts — Mar 25, 2026 · 9 min read
- When to Replace Your Cold Email Domains — Signs, Timing & Process — Mar 25, 2026 · 7 min read
- Cold Email for Marketing Agencies: How to Land Retainer Clients — Apr 5, 2026 · 8 min read
- The Outbound Sales Strategy Guide: Email, LinkedIn, and Phone in 2026 — Apr 5, 2026 · 9 min read
- The 15-Point Cold Email Deliverability Audit: Run This Before Every Campaign — Apr 5, 2026 · 10 min read
- ZeroBounce Pricing in 2026: Plans, Costs, and Is It Worth It? — Apr 5, 2026 · 10 min read
- MillionVerifier Pricing in 2026: The Budget Email Verification Option — Apr 5, 2026 · 9 min read
- Cold Email for E-commerce Suppliers: How to Get Your Products Into Online Stores — Apr 7, 2026 · 10 min read
Editorial process and review methodology are documented on the methodology page. For the rest of the editorial team see the about page.