Instantly.ai makes it dangerously easy to launch a cold email campaign. Connect a few inboxes, upload a CSV, write a sequence, hit start. What it doesn't do is protect you from the single most common cause of dead campaigns: a dirty list. Email industry data consistently shows that B2B contact data decays at 25-30% per year - meaning a lead list you scraped or exported even six months ago is already carrying a meaningful payload of dead mailboxes, and every one of them becomes a hard bounce the moment Instantly fires a send.
Bounce rate is the metric mailbox providers watch most closely when deciding whether your mail lands in the inbox or the spam folder. Google and Microsoft start degrading sender reputation when bounce rates creep past roughly 2%, and most cold email practitioners treat 3% as the absolute ceiling before a domain enters a reputation spiral it may not recover from. An unverified Apollo export typically bounces at 8-15%. That's not a deliverability problem - that's a domain funeral.
The fix is a five-minute workflow: verify your list *before* it ever touches Instantly. Across 50M+ emails processed, BounceZero's verification data shows that a typical scraped B2B list contains 12-18% invalid addresses, 15-25% risky catch-alls, and 3-6% role accounts - all of which you can identify and filter out for **$3 per 1,000 emails**, before a single send goes out.
This guide walks the full workflow end to end: exporting from Apollo, Clay, or LinkedIn scrapers; uploading to BounceZero's bulk verifier; interpreting the four result categories correctly; filtering with the right level of aggression for your risk tolerance; importing the clean file into Instantly; and configuring Instantly's own settings so your verified list stays protected throughout the campaign.
Why Verification Before Instantly Is Non-Negotiable
Instantly.ai is a sending engine, not a data-quality tool. It will faithfully deliver your sequence to every address in your CSV - including the 10%+ that no longer exist. Understanding what happens next explains why verification has to come first.
When Instantly sends to a dead mailbox, the receiving server returns a 550 hard bounce. That bounce is logged against the reputation of your sending domain and IP by every major mailbox provider. Email industry data puts the danger thresholds at roughly 2% bounce rate for early reputation damage and 5%+ for near-certain spam-folder placement across Google Workspace and Microsoft 365 recipients - which, in B2B cold email, is 80%+ of your list.
The math is unforgiving. Say you load 5,000 unverified Apollo leads into a campaign across four sending domains. At a typical 12% invalid rate, that's 600 hard bounces distributed across domains that are probably only weeks old and still warming. Each domain absorbs ~150 bounces against a few hundred total sends - a bounce rate north of 10%. Within days, open rates collapse from 50-60% to under 20%, replies flatline, and you're buying new domains and starting warmup from zero. Domain replacement plus 2-3 weeks of lost warmup time costs far more than the $15 it would have cost to verify all 5,000 emails at BounceZero's $3 per 1,000 rate.
There's a second-order effect most senders miss: spam traps. Data providers recycle addresses, and some scraped addresses are pristine traps seeded specifically to catch list buyers. Hitting even one Spamhaus trap can land your domain or IP on a blocklist that takes weeks to escape. BounceZero runs a dedicated spam trap detection check as one of its 6 verification layers (mailbox existence, catch-all 3-probe, role detection, disposable detection, MX validation, and spam trap screening), which is exactly the kind of filtering a sending tool like Instantly cannot do for you.
Instantly does offer its own built-in verification add-on, and it's better than nothing. But a dedicated verification engine exists for a reason: BounceZero's up to 99.8% accuracy in internal testing on SMTP-verifiable addresses against an industry benchmark of ~95% means roughly 30 fewer misclassified addresses per 1,000 verified. On a 20,000-lead campaign, that's ~600 addresses either wrongly bounced into your campaign or wrongly discarded from it. Verify first, with a dedicated tool, every time.
Step 1: Export Your Leads from Apollo, Clay, or LinkedIn
Your verification workflow starts at the export stage, and each lead source has quirks worth knowing.
Apollo.io. Apollo is the most common source for Instantly campaigns, and also the one that most needs verification. Apollo labels addresses as "Verified" or "Guessed," but that verification timestamp can be months old - and email industry data shows 2-3% of B2B addresses go dead *every month* as people change jobs. To export: build your list in Apollo, select your contacts, and use Export > CSV. Include at minimum the Email, First Name, Last Name, Company, and Title columns - Instantly will use these for personalization variables later. Pro tip: export Apollo's own email status column too; comparing it against BounceZero's results is a useful audit of your data source (in our verification data, 6-10% of Apollo "Verified" addresses come back invalid or risky on fresh verification).
Clay. Clay users typically enrich with waterfall providers (Prospeo, Datagma, Hunter, etc.), which means your email column is an aggregate of multiple sources with varying confidence. Export via Actions > Download CSV from your table view. Because waterfall enrichment often returns catch-all domains as "found," Clay lists tend to run high on the Risky category after verification - expect 20-30% catch-alls on a typical Clay export. Don't panic when you see it; Step 5 covers exactly how to handle them.
LinkedIn / Sales Navigator scrapers. Tools like Evaboot, Findymail, or Wiza scrape profiles and then guess-or-find emails. These lists are the highest-risk input of the three, because pattern-guessed emails ([email protected]) fail whenever a company uses a non-standard convention. Export the CSV from your scraper's dashboard and treat the entire file as unverified regardless of what the tool claims.
Before you move on, sanity-check the file:
A clean input file makes every downstream step - verification, filtering, and Instantly import - dramatically smoother.
Step 2: Upload Your CSV to BounceZero Bulk Verification
With your export ready, head to your BounceZero dashboard (create a free account at app.bouncezero.io/register if you don't have one - you get 100 free verifications per month with no credit card, enough to test the workflow before committing a full list).
The upload flow:
Processing is fast: dashboard jobs of up to 1,000,000 addresses complete in 5-10 minutes, and a typical 5,000-20,000 row cold email list finishes in well under five. You don't need to keep the tab open - you'll get an email when the job completes, and the dashboard shows live progress.
What's happening under the hood matters for how much you can trust the output. Each address passes through six independent checks: syntax and MX record validation (does the domain even accept mail?), mailbox existence via live SMTP conversation with the receiving server, catch-all detection using a 3-probe method (more on why that matters in Step 4), role account detection (info@, sales@, support@), disposable domain screening, and spam trap detection. This layered approach is what produces the up to 99.8% accuracy in internal testing on SMTP-verifiable addresses figure - single-check verifiers that only ping MX records or run one SMTP probe are where the industry's ~95% baseline comes from, and that 5% error margin is exactly the population that torches your Instantly campaigns.
A note on timing: verify as close to your campaign launch as possible. Verification results are a snapshot - accurate the moment they're taken, but subject to the same 2-3% monthly decay as any list. The gold standard workflow is: export Monday, verify Monday, import to Instantly Monday, launch Tuesday. If your verified list sits for more than 30 days before sending, re-verify it; at $3 per 1,000, a re-run costs less than a coffee and can save a domain.
If you'd rather automate this step - say, verifying leads as Clay enriches them - BounceZero's [real-time API](/api-email-validation) returns full verification results with timing that varies by provider and verification path, which slots neatly into a Clay HTTP-request column or a Make/Zapier flow before the lead ever reaches your CSV.
Step 3: Download and Read Your Results File
When the job completes, download the results CSV from the dashboard. BounceZero returns your original file with every column intact, plus verification columns appended - most importantly the status column, which assigns each address to one of four categories, and supporting columns like sub-status reason, whether the domain is catch-all, whether it's a role account, and whether it's disposable.
Here's what each status means in practice, with the distribution you should expect on a typical scraped B2B list based on BounceZero's verification data across 50M+ emails:
Valid (typically 55-70% of a scraped list). The mailbox exists, the domain's mail server confirmed it will accept mail for this exact address, and it passed all six checks. These are safe to send. Statistically, expect a residual bounce rate of ~0.2% on Valid addresses - the unavoidable noise of mailboxes deleted in the minutes or days between verification and send.
Invalid (typically 12-18%). The mail server explicitly rejected the address (550-class response), the domain has no MX records, or the mailbox is confirmed non-existent. These *will* hard bounce. There is no judgment call here: every Invalid address must be removed. Sending to even a fraction of them defeats the entire purpose of verifying.
Risky (typically 15-25%). The address couldn't be *disproven* but couldn't be positively confirmed either. The dominant sub-category is catch-all domains - mail servers configured to accept mail for any address at the domain, which makes a standard SMTP probe useless (the server says "yes" to everything, including gibberish). This bucket also includes role accounts and mailboxes on servers with aggressive greylisting. Risky is the category where senders make their biggest filtering mistakes, so Step 5 is devoted to it.
Unknown (typically 1-4%). The receiving server timed out, blocked verification probes entirely, or gave contradictory responses across retries. Some security-heavy corporate mail gateways (certain Proofpoint and Mimecast configurations) fall here by design. A well-run verifier keeps this bucket small - BounceZero's multi-probe retry logic and greylisting-aware re-checks typically hold Unknowns under 3%, versus 8-10% for verifiers that give up after one attempt.
Before filtering, glance at the summary stats on the results page. If your Invalid rate is above ~25%, your *data source* has a problem worth fixing upstream - no amount of verification makes a bad source good, it just quantifies the damage.
Step 4: How Catch-All Detection Actually Works (and Why It Matters for Cold Email)
Catch-alls deserve their own step because they're the largest gray zone in any cold email list - and because how your verifier handles them directly determines how much sendable volume you keep.
A catch-all (accept-all) domain is a mail server configured to accept delivery for *any* local part: [email protected] and [email protected] both get a 250 OK at the SMTP level. Roughly 20-30% of B2B domains run catch-all configurations according to email industry data, and the share is higher among companies using Microsoft 365 with certain gateway setups. For a verifier, this breaks the naive approach: you can't confirm a specific mailbox exists just because the server accepted it.
Cheap verifiers respond in one of two bad ways. Either they mark every catch-all address "valid" (inflating your list with addresses that may silently bounce or, worse, deliver to a void), or they dump them all in "unknown" (throwing away potentially 25% of your addressable market). Both are lazy answers to a hard problem.
BounceZero's 3-probe catch-all method goes further. Instead of a single RCPT TO check, it runs a sequence of probes against the domain: verifying the target address, then testing deliberately fabricated addresses at the same domain, and comparing server behavior - response codes, response timing, and rejection patterns - across all three. Many "catch-all" servers actually leak signal: they accept everything at the SMTP handshake but respond measurably differently (timing deltas, downstream filtering behavior, tempfail patterns) for real versus fake mailboxes. Combined with domain-level intelligence - MX provider fingerprinting, DMARC posture, domain age and web presence - this lets BounceZero resolve a meaningful share of catch-all addresses into confident Valid or Invalid classifications rather than punting them all to Risky.
The practical impact on your Instantly campaign: on a typical 10,000-lead list with 2,500 catch-all addresses, single-probe verifiers force you to make one blanket decision about all 2,500. BounceZero's approach typically resolves 30-40% of those into a definitive status, leaving a smaller, honestly-labeled Risky pool - and for that remaining pool, the results file includes the catch-all flag and domain intelligence so you can segment intelligently rather than guess.
One more nuance worth knowing: a *Valid result on a non-catch-all domain* is the strongest signal in email verification - the server had every opportunity to reject the address and specifically confirmed it. When you see Valid + catch_all=false in your results, that address is about as certain as email verification gets. This distinction becomes useful in the next step when you decide how aggressive to be with filtering.
Step 5: Filter Your Results - What to Keep, Cut, and Segment
Now the decision step. Open the results CSV (or use the dashboard's built-in export filters, which let you download pre-filtered segments directly) and apply these rules:
Always remove - no exceptions:
Remove for cold email specifically:
The judgment call - Risky/catch-all addresses:
This is where your risk tolerance and infrastructure maturity come in. Three sane strategies:
Conservative (fresh domains, first campaigns): Send only Valid. Your bounce rate will land around 0.2-0.5%, your warming domains stay pristine, and you sacrifice reach for safety. Right call for domains under 60 days old.
Balanced (recommended for most senders): Send Valid immediately. Put Risky catch-alls into a *separate Instantly campaign* on your most-warmed, most-expendable domain, at reduced daily volume (10-15 sends/inbox/day instead of 25-30). Real-world catch-all bounce rates typically run 2-5% - survivable when isolated, dangerous when blended into your main campaign's stats. This quarantine approach means a bad catch-all cluster damages one domain's reputation, not your whole fleet.
Aggressive (mature infrastructure, high-value targets): Same as Balanced, but also segment catch-alls by signal quality using the extra columns in your results file - catch-alls at domains with strong web presence, valid DMARC, and established MX providers bounce far less than catch-alls at thin, newly-registered domains.
Unknowns: treat like Risky at low volume, or simply drop them - at 1-3% of the list, they're rarely worth agonizing over.
The outcome: from a 10,000-lead raw export, expect to end with roughly 6,000-7,000 Valid sends plus an optional 1,500-2,000 quarantined Risky sends. Yes, the list shrank - but the 3,000 addresses you cut were never going to reply. They were only ever going to bounce, complain, or vanish into the void while taking your sender reputation with them. You can quantify exactly what those prevented bounces are worth to your program with our [ROI calculator](/roi-calculator).
Save your filtered output as a fresh CSV - e.g. campaign-valid-2026-07.csv - keeping the name, company, and title columns Instantly needs for merge variables.
Step 6: Import Your Clean List into Instantly.ai
With a verified, filtered CSV in hand, the Instantly import takes two minutes - but a few settings during import are worth getting right.
The import flow:
If you're running the Balanced strategy from Step 5, create a second, separate campaign for your Risky/catch-all segment now. Duplicate your main campaign's sequence, assign only your designated "quarantine" sending accounts to it, and import the risky CSV there. Keeping the segments in separate campaigns - rather than separate lead labels within one campaign - is what keeps their bounce statistics, and their reputational blast radius, isolated.
One workflow habit that pays off: name your campaigns with the verification date, e.g. "SaaS CTOs - verified 2026-07-07." When you revisit a paused campaign in September and wonder whether the list is still trustworthy, the answer is in the name. Any verified list older than 30-45 days should go back through [bulk verification](/bulk-email-validation) before you resume sending - at $3 per 1,000 and 5-10 minutes of processing, re-verification is the cheapest insurance in cold email.
Step 7: Instantly Settings for Bounce Protection After Verification
Verification before import removes the vast majority of bounce risk, but the residual matters - mailboxes die between verification and send, and your quarantined catch-all segment carries known risk. Configure Instantly to make the remaining risk self-limiting:
1. Set a campaign bounce-rate stop. In your campaign settings, enable the option to auto-pause the campaign when bounce rate crosses a threshold. Set it to 3% for your Valid-only campaign (it should never trigger; if it does, something upstream is wrong and you *want* the hard stop) and 5% for the catch-all quarantine campaign. This is your circuit breaker - a campaign that pauses itself at 3% is annoying; a campaign that runs all weekend at 12% is a dead domain.
2. Cap daily sending volume per account. Keep each sending inbox at 25-30 cold emails per day maximum for established accounts, and 10-15 for accounts under 30 days of warmup. Verification doesn't change provider volume heuristics: Google's spam filtering weighs sudden volume spikes independently of bounce rate. For the quarantine campaign, stay at the low end regardless of account age.
3. Keep warmup running alongside campaigns. Leave Instantly's warmup enabled on every sending account at a meaningful ratio - warmup engagement (opens, replies, spam-folder rescues) actively offsets the neutral-to-negative signals cold sends generate. Accounts that stop warming when campaigns start show measurably faster reputation decay in the weeks that follow.
4. Enable stop-on-reply and stop-on-auto-reply handling. Beyond the obvious courtesy, out-of-office auto-replies are a data signal: an OOO with a "no longer with the company" message means that address is about to become a bounce for everyone else. Instantly can detect these; prune them.
5. Randomize sending intervals. Use Instantly's gap settings (e.g., 8-15 minutes between sends per account) rather than metronomic sending. Uniform timing is a classic automation fingerprint.
6. Monitor the first 48 hours closely. After launch, check the campaign analytics twice daily for the first two days. Healthy post-verification numbers look like: bounce rate under 1% on the Valid segment, opens 45-65% (where tracking is enabled), and no single sending account diverging sharply from the others. One account bouncing while siblings are clean usually indicates an account-level or domain-level problem, not a list problem.
7. Feed bounces back into your data hygiene. Export any bounces Instantly does record and check them against your BounceZero results file. A bounce on an address verified Valid days earlier is almost always post-verification mailbox churn (expect ~0.2%). A cluster of bounces from one domain in your catch-all segment means that domain's server accepts-then-rejects - blocklist the domain in your data source so it never re-enters your pipeline.
With verification upstream and these guardrails inside Instantly, your bounce rate stops being a threat you monitor anxiously and becomes a boring number that sits under 1%.
The Complete Workflow, Recapped - and What It Costs
Here's the entire pipeline in one place, timed against a realistic 10,000-lead campaign:
1. Export (10 min): Pull your CSV from Apollo, Clay, or your LinkedIn scraper with email, first name, company, and title columns. Treat every export as unverified regardless of source claims.
2. Upload (2 min): Drag the CSV into BounceZero's bulk verifier. Cost for 10,000 emails: $30 at $3 per 1,000, with duplicates deduplicated free before billing.
3. Verify (5-10 min): Six checks per address - mailbox existence, 3-probe catch-all analysis, role detection, disposable screening, MX validation, spam trap detection - at up to 99.8% accuracy in internal testing on SMTP-verifiable addresses. Grab a coffee.
4. Filter (10 min): Delete Invalid, disposable, spam-trap, and role addresses. Keep Valid for the main campaign. Quarantine catch-alls into a separate segment or drop them, per your risk tolerance.
5. Import (5 min): Load the clean CSV into Instantly, confirm variable mapping, enable cross-campaign duplicate checking, and set up the quarantine campaign if you're sending to catch-alls.
6. Configure (5 min): Bounce-rate auto-pause at 3%, volume caps at 25-30/inbox/day, warmup left running, stop-on-reply enabled, randomized send gaps.
Total: under 45 minutes and $30 to convert a list that would have bounced at 10%+ into one that bounces under 1%.
Now weigh that against the alternative. A burned sending domain costs ~$10-15 to replace, but the real cost is time: 2-3 weeks of warmup before the replacement can carry volume, plus the pipeline gap while your campaign sits dark. For a team whose cold email sources even two meetings a week, a three-week outage across a domain fleet is thousands of dollars in lost pipeline - traded against a $30 verification run and 45 minutes of process. Across 50M+ verified emails, this is the most consistent pattern in BounceZero's data: the senders with the longest-lived domains aren't the ones with the best copy or the fanciest infrastructure. They're the ones who never send to an unverified address.
If your volume justifies automating the whole thing, the [BounceZero API](/api-email-validation) verifies addresses in provider-dependent response time, which means you can verify at the enrichment layer - inside Clay, inside your CRM webhook, inside a Make scenario - so that no unverified address ever reaches a CSV in the first place. And if you want to test the workflow before spending anything, the free tier's 100 verifications per month requires no credit card.
Frequently Asked Questions
Should I use Instantly's built-in verification or BounceZero?
Use a dedicated verifier before import as your primary check. Instantly's built-in verification is a convenience layer, and like most bundled checkers it operates around the industry-typical ~95% accuracy range - meaning roughly 50 misclassifications per 1,000 addresses, split between bad emails let through and good emails wrongly discarded. BounceZero's up to 99.8% accuracy in internal testing on SMTP-verifiable addresses comes from running six independent checks per address, including 3-probe catch-all analysis and spam trap detection that sending tools don't attempt. Pre-verifying with BounceZero and skipping Instantly's paid add-on is also usually cheaper. The one scenario where a light second check adds value: if your verified list sat unused for more than 30-45 days before launch - though at that point, a $3-per-1,000 re-run through BounceZero is the better fix.
Should I send to catch-all (Risky) emails in my cold campaigns?
It depends on your infrastructure maturity. On fresh domains (under 60 days) or your first campaigns: no - send only Valid addresses and accept the smaller list. On established infrastructure: yes, but quarantined. Put catch-alls in a separate Instantly campaign on your most-warmed, most-expendable sending domain, at reduced volume (10-15 sends/inbox/day), with a 5% bounce auto-pause. Real-world catch-all bounce rates run 2-5% - manageable when isolated, damaging when mixed into your main campaign. Note that BounceZero's 3-probe catch-all method resolves 30-40% of catch-all addresses into definitive Valid/Invalid classifications that single-probe verifiers can't, so your Risky bucket is smaller and more honestly labeled to begin with.
How old can a verified list be before I need to re-verify?
Treat 30 days as the practical shelf life for cold email, and 45 days as the hard ceiling. Email industry data shows B2B addresses decay at roughly 2-3% per month as people change jobs and companies restructure mail systems - so a list verified 60 days ago has quietly accumulated 4-6% new invalid addresses, enough on its own to push you past the 3% bounce threshold that damages sender reputation. Re-verification is deliberately cheap insurance: $3 per 1,000 emails, with a 10,000-row file processing in 5-10 minutes through bulk verification. Date-stamp your Instantly campaign names with the verification date so you never have to guess whether a paused campaign's list is still trustworthy.
What bounce rate should I expect in Instantly after verifying with BounceZero?
On the Valid-only segment, expect roughly 0.2-0.5% - residual bounces from mailboxes that died in the window between verification and send, which no verifier can eliminate. That's comfortably under the ~2% threshold where Google and Microsoft begin degrading sender reputation. If you're also sending to a quarantined catch-all segment, expect 2-5% on that campaign specifically, which is why it belongs on isolated sending domains. If your Valid segment bounces above 1-2%, investigate before assuming a verification failure: the most common culprits are a stale list (verified more than 30 days before sending), a mis-mapped email column during Instantly import, or sending-domain reputation problems being misreported as recipient bounces.
Can I automate verification so I don't have to run CSVs manually?
Yes, and at meaningful volume you should. BounceZero's real-time API returns full verification results - status, catch-all flag, role/disposable detection, spam trap screening - with timing that varies by provider and verification path on average, fast enough to sit inline in an enrichment pipeline. Common setups: an HTTP-request column in Clay that verifies each email the moment the waterfall finds it, a Make or Zapier step between your lead source and your Instantly campaign (Instantly's API lets you push verified leads directly into campaigns, skipping CSVs entirely), or a webhook on CRM contact creation. The API docs at /api-email-validation cover authentication and response schema; a single verified-at-enrichment pipeline means no unverified address ever reaches a campaign.
How much does it cost to verify a typical cold email list?
BounceZero charges $3 per 1,000 verifications, so a 5,000-lead list costs $15, a 10,000-lead list $30, and a 50,000-lead list $150 - with duplicates deduplicated free before billing, and bulk dashboard jobs up to 1,000,000 addresses processing in 5-10 minutes. For context on ROI: a single burned sending domain costs $10-15 to replace plus 2-3 weeks of warmup before it can carry volume again, and an unverified list bouncing at a typical 10-15% will reliably burn domains within days. Most cold email teams find verification pays for itself the first time it prevents one domain from entering a reputation spiral. There's also a free tier - 100 verifications per month, no credit card - to test the workflow, and the /roi-calculator quantifies the savings against your specific volumes.
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