A hard bounce is permanent — the address does not exist. A soft bounce is temporary — the mailbox was full or the server was busy. Fuzegenai treats them very differently: a hard bounce suppresses the address for good, a soft bounce does not.
How the two are told apart
The rejection text from the receiving server decides it.
- Hard: "user unknown", "address not found", "domain not found", "recipient rejected", and SMTP codes 550, 551, 553.
- Soft: "mailbox full", "quota exceeded", "message too large", "temporary failure", and SMTP codes 421, 450, 451, 452.
If the reason is unclear, it is treated as a hard bounce. That is deliberate — guessing wrong in the other direction costs you reputation.
What happens to the lead
On a hard bounce:
- The lead is marked bounced.
- Any remaining queued emails for that lead in that campaign are cancelled.
- The address is added to your organisation's suppression list with the reason Hard bounce, so no future campaign can email it.
On a soft bounce the lead is marked soft-bounced, nothing is suppressed and nothing is cancelled.
Both count against the sending mailbox's reputation. A soft bounce counts half. See Mailbox health and sender reputation.
The 3% auto-pause
If an active campaign's bounce rate goes above 3% — measured once it has at least ten sends — the campaign is paused for you, and the campaign page shows Campaign Auto-Paused with the rate it hit. Clean the list before you resume.
You can switch this off per campaign with Disable BounceProtect in the campaign's options, but a rate that high is already doing damage. Fix the list instead.
Where to see bounces
- Suppression & frequency caps — the Records tab lists every suppressed address; filter the reason to Hard bounce. Eligibility Checker tells you whether one specific address is allowed to receive sends. You can also Add record, Import CSV and Export CSV.
- Global Analytics, on the email tab — the Bounce Reasons card and the Bounced tile.
- Email Accounts — the Rates 7d column shows each mailbox's own bounce rate and turns red above 5%.
The Auto-rules tab on the suppression page lets you set thresholds for automatic suppression after repeated bounces, complaints or unsubscribes.
Email verification
Fuzegenai verifies addresses for you rather than asking you to run a separate check. Email verification has the overview. When you launch a campaign, every lead that has not been checked yet goes through three layers: address syntax, whether the domain accepts mail at all, then a mailbox-level check. Results are Verified, Invalid, Catch-all, Risky or Unverified.
Addresses that come back invalid are suppressed before they can bounce. A result is cached for your organisation, so the same address is not re-checked in every campaign.
Role-based addresses such as info@, admin@ and support@ are skipped by default, because they bounce and generate complaints more than anything else in cold outreach. The Allow Risky Emails setting in a campaign's options controls that.
Reducing bounces
Keep lists fresh and never re-import an address that has already hard bounced. If the bounce rate is high across every campaign, the list source is the problem rather than the settings. Write to priority@fuzegenai.com if the numbers look wrong to you.