Keep your Sailthru user list clean and deliverable
Sailthru suppresses an address the moment it hard-bounces and honors every opt-out level, so it reacts fast to a mailbox that has already failed — but it can't judge an address it has never sent to, and those never-mailed invalids from imports and signup forms are what quietly erode your deliverability. Qualisend closes that gap: connect Sailthru directly through the live native connector to verify and clean your user lists in place, or run the export-verify-suppress loop by hand. The REST API and no-code flows through Zapier, Make, and n8n cover everything in between.
Connect Sailthru and clean it in place
Connect Sailthru with an API key and Qualisend verifies the lists you already have — right inside Sailthru, no export. Dead and risky addresses are suppressed or archived for you, every new subscriber is checked in real time, and you can re-verify on a schedule so the list never drifts back to dirty.
Prefer to work by hand, or verify at signup through your own stack? The CSV export → verify → reimport loop below and the REST API are fully supported too.
Connect SailthruWhat Sailthru cleans for you
Sailthru's native hygiene runs on hardbounce detection and its opt-out model. When an address hard-bounces, Sailthru flags the user and stops mailing it, and you can wire a Hardbounce Postback to be notified the moment it happens. On top of that, every user carries an opt-out status: Optout (All) removes them from every message including transactional receipts and password resets, while Optout (Marketing) removes them from campaigns but still allows those basic transactional sends. For addresses Sailthru has actually mailed, that combination is reliable automatic hygiene.
What it can't catch
The catch is that all of it is reactive — it needs a real send and a returned bounce to fire. Never-mailed invalids from imports and signup forms, disposable addresses accepted at capture, role addresses like info@ and support@, decayed mailboxes that have gone dark, and catch-all domains that accept everything at SMTP time all look like valid users until your first blast proves otherwise — which is exactly when Gmail and Yahoo form their first impression of your sending domain. An imported list is the sharpest case: it arrives with its bounce history stripped, so an address that was already failing on another platform looks brand new to Sailthru.
Why a clean Sailthru list matters
Sailthru is enterprise software, and enterprise contracts are commonly sized on active-user counts or send volume, so a list padded with addresses you'll never reach quietly inflates what you renew on. The bigger stake is reputation: your first blast to an unverified list is where Gmail and Yahoo — under their 2024 bulk-sender rules, which demand a spam-complaint rate below 0.3% and punish repeated bounces — decide how your domain gets treated, and Sailthru's own deliverability monitoring reads the same signals. A single send to a stale imported list can undo months of good sending history. Cleaning before the send protects both the cost of your contract and the inbox placement of the campaigns that actually convert.
Prefer CSV or the API? Here's the manual path
The native connector is the fastest route, but the CSV loop works on any Sailthru plan: export from Sailthru, verify in Qualisend, and act on the results.
Export your list from Sailthru
Open the Lists page and click the spreadsheet icon on the row for the natural or smart list you want to clean. Export to CSV — you can pull email only or include user vars and opt-out data.
Verify the file in Qualisend
Upload the CSV to Qualisend bulk cleaning — up to 1,000,000 addresses per job with live progress, duplicates charged once — or paste addresses directly. The free plan's 100 credits, which never expire, cover a first sample.
Read the results
Every address returns deliverable, risky, undeliverable, or unknown with a reason code and sub-flags (catch-all, disposable, role, full mailbox), plus the MX provider and SMTP probe detail as evidence and a 0–100 confidence score. Download the cleaned CSV.
Retire the undeliverables in Sailthru
Filter your results to undeliverable and set those users to Optout (All) so they're suppressed from every send — one profile at a time in the UI, or in bulk through the user Job API. Opt-out is enough to protect deliverability; delete the user only when you need a full GDPR-style forget.
Or automate it at signup
Prefer to keep junk out from the start? Verify at the point of capture with the Qualisend REST API (scoped keys, rate limits, webhooks) or a Zapier, Make, or n8n flow, so a new signup is checked before it ever reaches Sailthru or a blast. The live native connector also verifies new contacts in real time and can re-clean your lists on a schedule.
What Qualisend flags on every address
- Never-mailed invalid addresses that would hard-bounce on your next blast and trip Sailthru's hardbounce suppression
- Disposable and throwaway domains built to expire days after signup
- Role addresses like info@ and support@ that skew the engagement Sailthru's segments and Lifecycle Optimizer read
- Catch-all domains that accept everything at SMTP time, flagged so you can segment and throttle them instead of blasting blind
- A 0–100 confidence score and machine-readable reason code on every address, so borderline calls are yours to make
The native Sailthru connector is live — connect it in Qualisend under Integrations and clean your list without a single CSV. New contacts are verified automatically, and you can re-verify on a schedule.
What to do with each result
Every address comes back with a verdict and sub-flags. Here's the action that keeps your Sailthru list clean without throwing away contacts you can still reach.
deliverableKeep sending as normal.deliverable + role flagKeep for basic transactional sends; exclude from engagement-judged blasts and segments.risky + catch-all flagMove to a dedicated list or segment and throttle your sends.risky + disposable flagSet Optout (All) or delete — the inbox was built to expire.unknownKeep active and re-verify next clean — usually greylisting or rate-limiting, not a verdict on the mailbox.undeliverableSet Optout (All) now, or delete for a full forget; don't wait for the bounce to prove it.Related reading
How verification, authentication, and engagement combine to land in the Sailthru inbox.
Why a clean list before your first blast protects the domain reputation Sailthru sends on.
The 2024 bulk-sender bounce and complaint thresholds every Sailthru send is judged against.
A cadence for re-verifying Sailthru lists so decayed mailboxes don't pile back up.
Verify at signup with scoped keys and webhooks so junk never enters Sailthru.
Sailthru verification FAQ
Clean your Sailthru list in minutes
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