Above 2% bounce rate, Gmail and Outlook throttle your domain. Here's how to get below 0.5% — and stay there.
Upload your list to BounceZero. Remove all Invalid, Disposable, and Role addresses. This eliminates the 5–15% of addresses on unverified lists that would hard-bounce. For a 50,000-address list, verification takes about 5 minutes.
Send a confirmation email immediately after signup. Only add the contact to your list when they click the link. Double opt-in eliminates typos and fake entries — the two biggest sources of new hard bounces from organic acquisition.
Add every 5xx hard-bounced address to a global suppression list the moment the bounce occurs. Never mail them again — even if they re-appear in a CRM import, list purchase, or data merge months later.
Register with Google Postmaster Tools (Gmail reputation + spam rate), Microsoft SNDS (Outlook/Hotmail reputation), and Yahoo Postmaster. Set up alerts. Reputation damage compounds — act within 24 hours of a score drop.
New IPs have no reputation. Ramp volume 20–30% per day over 4–6 weeks. High volume from a cold IP triggers 4xx soft bounces even to valid addresses. Hitting a reputation wall early can take months to recover from.
Email addresses expire at roughly 2% per month for corporate domains (employees leave). A 6-month-old list can have 12%+ new invalids compared to when it was collected. Always re-verify before re-engaging dormant segments.
| Bounce Rate | Status | ISP Behaviour |
|---|---|---|
| < 0.3% | Excellent | Full inbox placement, strong sender reputation |
| 0.3% – 0.5% | Good | Healthy — monitor but no action needed |
| 0.5% – 1% | Warning | Reputation at risk — verify and clean list now |
| 1% – 2% | Danger | Gmail/Outlook may begin throttling or soft-blocking |
| > 2% | Critical | Active throttling, bulk folder placement, possible suspension |
| > 5% | Blacklist risk | IP/domain reputation severely damaged — recovery takes weeks |
The target is below 0.5% bounce rate per campaign. Gmail and Outlook begin throttling senders above 2%. Most ESPs warn accounts above 2% and suspend above 5%. With verification + double opt-in, below 0.3% is achievable.
Common causes: purchased or scraped lists (10–30% invalid), list age without re-verification (2% decay per month), no double opt-in (allows typos + fake entries), not suppressing previous hard bounces, and merging CRM data without verification.
Corporate emails expire 30–90 days after an employee leaves. Consumer addresses decay 15–25% per year. A 6-month-old list can have 10–15% more invalid addresses than when collected.
Verification eliminates hard bounces from invalid addresses — typically 5–15% of unverified lists. Catch-all domains remain a source of potential bounces; BounceZero flags these as Risky with a confidence score for risk-based sending decisions.
Upload your list to BounceZero. Verification runs at ~10,000 emails per minute. Remove all Invalid results before sending. A 50,000-address list takes ~5 minutes and typically drops bounce rate from 5–15% to under 0.3%.
100 free credits. ~10,000 emails per minute. Results in seconds.
Start Free — No Card NeededDeep-dive guides on how email verification and inbox placement work
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The RCPT TO handshake explained — codes, catch-alls, limits
Why domains accept everything and how ML classifies deliverability
Temp addresses, how to detect them, and why they matter
Hard vs soft bounces, SMTP codes, and how to fix them
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