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.
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True catch-all is 1.4% - most of what looks catch-all is unprobeable providers
info@ bounces 4.5x more than personal addresses - measured, not guessed
The 3x invalid-rate gap that vanishes when you control for domain size
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