Your email closing measurably affects whether you get a reply — and the data points to one clear winner. Boomerang's 2017 analysis of over 350,000 email threads found that "Thanks in advance" achieved a 65.7% response rate, while generic closings like "Best" plateaued at 51.2%. That's a 14.5 percentage-point difference — or roughly a 28% relative increase, as Boomerang framed it — driven entirely by your final sentence.
Even the simpler gratitude options beat neutral sign-offs by a meaningful margin. "Thanks" came in at 63%, which is 11.8 percentage points ahead of "Best" (51.2%). "Thank you" landed at 57.9% — still 6.7 percentage points above "Best." The pattern is consistent: gratitude outperforms neutrality, every time.
From the same single Boomerang study, when researchers grouped all emails with any thankful closing together, those emails saw a 62% response rate versus 46% for emails without a thankful closing. That's a 36% relative increase in average response rate. Gratitude creates psychological goodwill — it triggers reciprocity, and the data backs it up.
One important caveat: Boomerang's data comes from mailing list archives of online communities — warm, community-based email threads, not cold outreach. The absolute response rates (65.7%, 63%, etc.) won't translate to your cold email sequences. What does transfer is the relative ranking: gratitude-based closings consistently outperform neutral ones, regardless of context. So don't expect 65% reply rates on cold email — but do expect gratitude sign-offs to outperform "Best regards" in your campaigns too.
Speaking of cold email benchmarks: the real-world numbers are humbling. According to Pipeful/Belkins' 2024 study of over 13 million B2B emails, the average cold email response rate is 5.1%. Cleanlist's 2026 aggregated benchmark puts the average even lower at 3.1% (with top performers hitting 8–12%). These figures reflect different methodologies and timeframes, so treat them as two data points rather than a single consensus — but either way, the baseline is far from the community-email numbers above.
List quality compounds everything. According to Cleanlist — an email verification service, so weigh this with that context in mind — verified email lists get roughly 2x the reply rate of unverified lists and 5–6x the reply rate of purchased lists. Your sign-off won't save you if your list is full of bad addresses. Fix your data quality first, then optimize your closing.
The bottom line: ditch "Best regards" and default to gratitude. "Thanks in advance" is the top performer, but even a plain "Thanks" or "Thank you" beats neutral closings by a statistically meaningful margin. It's not just polite — it's the highest-leverage word choice at the end of your email.
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Sources
- LaGrowthMachine — How to End an Email That Requires a Response: 12 Proven Sign-Offs
- Boomerang Blog — Forget "Best" or "Sincerely," This Email Closing Gets the Most Replies (2017)
- LinkedIn / Pipeful — What are B2B Cold Email Response Rates? (2024 Study)
- Cleanlist — Cold Email Response Rate Statistics (2026)