Start with Your Bounce Rate Tolerance
Before setting a threshold, know your acceptable bounce rate. Email service providers and mailbox providers use bounce rates as one signal for sender reputation scoring. Most professional senders aim to keep their bounce rate below 2 percent. Some ESPs will suspend accounts that exceed 5 percent on a campaign. If your sender reputation is already strong, you have more room to test mid-range confidence scores. If it is under pressure, be conservative.
A helpful calculation: if 30 percent of your list is catch-all and you send to everything above a score of 50, what is the likely bounce rate from that segment? Multiply the proportion of addresses in that score band by an estimated bounce rate for that band, add it to your non-catch-all bounce rate, and check whether the total stays within your limit.
Decision Framework by Campaign Type
Cold Outreach (No Prior Engagement)
Cold campaigns carry the highest risk. You have no prior signal that the contact monitors the address, and a bounce from a cold contact is a pure reputation hit with no upside.
Recommended threshold: send to scores of 75 and above. Suppress everything below.
Warm Campaigns (Prior Engagement or Opt-In)
If the contact has previously opened an email, clicked a link, filled in a form, or opted into communication, the engagement history provides a signal that the address is monitored. This lowers the risk of sending to medium-confidence catch-all addresses.
Recommended threshold: send to scores of 50 and above for engaged contacts.
Re-Engagement Campaigns
For contacts who previously engaged but have gone quiet, a re-engagement campaign to catch-all addresses in the 40 to 60 score range is defensible if the campaign is small and the potential value of reactivation is high. Keep these sends low-volume and monitor delivery rates closely on the first campaign.
HCP and Pharmaceutical Outreach
Hospital and clinic domains are heavily catch-all, and the contacts in HCP campaigns are high-value targets with limited substitutes. Most pharma and medical device teams in EmailAddress.ai's customer base send to HCP catch-all addresses at a threshold of 60 or above, accepting a somewhat higher bounce rate from this segment in exchange for broader list coverage.
If the HCP contact record was sourced from EmailAddress.ai's licensed HCP data, the monthly refresh process has already cleared addresses that showed persistent non-delivery. In that case, the confidence score is a second validation layer rather than the primary quality signal.
Segmenting Your List by Confidence Tier
Rather than a single send/suppress cutoff, consider segmenting catch-all addresses into tiers and treating each differently:
- Tier 1 (score 80+): Send with standard cadence and content. Treat identically to verified deliverable addresses.
- Tier 2 (score 60 to 79): Send with a slightly simplified email (fewer images, smaller payload). Monitor delivery rates on the first send.
- Tier 3 (score 40 to 59): Send only in warm campaigns or high-value HCP contexts. Watch bounce rates carefully.
- Tier 4 (below 40): Suppress for most campaign types. Store in a re-verification queue for review in 60 to 90 days.
Managing Suppression Lists
Catch-all addresses that receive a hard bounce should be immediately added to your suppression list, exactly as you would handle a confirmed invalid address. The confidence score told you the delivery was likely but not certain; the bounce confirmed the outcome. Remove those addresses and do not re-verify them unless the contact's information is updated through a new data source.
Soft bounces on catch-all addresses deserve more careful handling. A soft bounce (a 4xx temporary error) may reflect greylisting rather than a bad address. See greylisting explained before suppressing soft-bounced catch-all addresses.
Re-Verifying Catch-All Segments
Confidence scores reflect the state of a domain's infrastructure at the time of verification. Domain configurations change. An address that scored 45 three months ago may score 75 today if the organization updated its mail server software. Re-verifying suppressed catch-all segments every 60 to 90 days surfaces contacts that have moved into a sendable confidence tier.
Frequently Asked Questions
What happens to my sender reputation if I send to low-confidence catch-all addresses?
+
Sending to low-confidence catch-all addresses increases your bounce rate, which is one of the signals mailbox providers use to evaluate sender reputation. A sustained bounce rate above 2 to 3 percent from catch-all sends can result in throttling, filtering to spam folders, or account suspension at some ESPs. Use the confidence score to limit catch-all sends to segments where the estimated bounce rate keeps your overall campaign below your provider threshold.
Should I suppress all catch-all addresses?
+
No. Suppressing all catch-all addresses means discarding 25 to 45 percent of a typical B2B list, including many addresses that are genuinely deliverable. The confidence score lets you distinguish high-probability addresses from low-probability ones. Suppressing only the low-confidence segment (scores below 50 or your chosen threshold) recovers significant list coverage without the full bounce risk of sending to everything.
Can I re-verify suppressed catch-all addresses?
+
Yes, and it is often worth doing every 60 to 90 days. Domain configurations change over time, and an address that was low-confidence previously may score higher on re-verification if the organization updated its mail server or configuration. Addresses that received a hard bounce should remain suppressed; those that received no response or a soft bounce during a prior attempt can reasonably be re-verified.
What threshold do most teams use for cold outreach?
+
Based on usage patterns across EmailAddress.ai customers sending cold B2B campaigns, the most common threshold for catch-all cold outreach is 75. Teams sending to known HCP contacts with licensed data often use 60. Teams under active deliverability pressure hold at 80 or above until reputation metrics stabilize.
Ready to verify catch-all addresses?
EmailAddress.ai scores individual addresses within catch-all domains so you can send with confidence instead of suppressing your entire B2B or HCP list.