Verify every recipient before Mailjet's Send API ever touches it
Mailjet automatically blocks an address once it hard-bounces or draws a spam complaint, holding it back for 90 days so it can't fail twice - but for a transactional sender that protection only fires after the first bad send, and the first send is exactly where the reputation damage is done. Because Mailjet is an API/SMTP sender, the leverage for transactional mail is verifying every address before the Send API ever touches it. Qualisend closes that gap: verify at the point of capture and again before any batch send, so an invalid address never reaches your sending in the first place. For contacts and lists stored in Mailjet, the native connector verifies them in place and saves each result as a contact property. Here's how, plus the API and no-code options.
Connect Mailjet directly, no CSV needed
Connect with an API key
Enter your Mailjet API key and Secret key. Find both in Mailjet under Account settings → REST API → API Key Management.
- Clean all contacts or a single list
- Results saved as properties on each contact
- Or verify and export a clean list
- Auto-clean every 7, 14 or 30 days
Prefer CSV or the API? Both work too, see below.
What Mailjet cleans for you
Mailjet's native hygiene runs on its automatic block. The moment an address hard-bounces - an invalid or non-existent mailbox, or a server Mailjet can't deliver to - it's automatically "preblocked" and held out of every send for 90 days, the idea being to protect your sender reputation by never letting the same address fail twice; addresses that draw a spam complaint are preblocked the same way. That block is global to Mailjet's platform - an address that hard-bounced on another customer's send can be blocked for yours - and, crucially, it applies to everything, including the Send API, so once Mailjet has seen an address fail it won't be mailed again by your transactional stream either. Mailjet also offers a manual Campaign Exclusion List, but that one only holds contacts out of marketing campaigns and automations (automation emails count as marketing) - the Send API still delivers to an excluded address by design - so it does nothing to shield a transactional send. For addresses Mailjet has actually sent to and seen fail, that automatic block is reliable hygiene.
What it can't catch
The catch is that every one of those mechanisms is reactive - it needs a send, and then a bounce or complaint, to fire. Never-verified invalids from your signup and checkout forms, disposable addresses, role addresses, and mailboxes that have quietly decayed have never bounced because Mailjet has never sent to them, so there's no block on them - the Send API will happily deliver into a hard bounce on the very first attempt, and only then block the address for 90 days, after the damage is done. Transactional streams are the sharpest case: a password reset or receipt fires automatically to whatever the user typed, and the Campaign Exclusion List can't pre-empt it because it doesn't apply to the Send API. The only thing standing between a mistyped address and a first-send hard bounce is verification before the call.
Why a clean Mailjet list matters
Mailjet bills on the emails you send each month, not on how many contacts you store - its higher plans carry unlimited contacts - so a dead address doesn't inflate a contact tier the way it would on a subscriber-priced platform. The cost of a bad address here is twofold. First, the wasted send: every invalid you deliver to burns one of your monthly sends and, once you're over your allowance, bills as an overage at renewal - you're paying to hard-bounce. Second, and far more important for a transactional sender, is reputation. Transactional mail is your most reputation-sensitive stream - it rides a dedicated IP or a shared pool you depend on for password resets and receipts - and a spike of first-send hard bounces is exactly what Gmail and Yahoo's 2024 sender rules, and Mailjet's own bounce-rate limits, penalize. Push your bounce rate too high and Mailjet will throttle or block your sending outright; when that happens, it's your account emails, not a marketing blast, that stop reaching the inbox. Verifying before the send keeps the bounce off your record entirely.
Prefer CSV or the API? Here's the manual path
Mailjet is a transactional/API sender, and the connector covers only the contacts and lists stored in Mailjet - so for Send API traffic the honest path is to verify every address before the Send API touches it: in real time as it's captured, and again before any batch send.
Verify at the point of capture
Call the Qualisend REST API from your signup, checkout, or account form and check the address before it's written to your database. A mistyped or disposable address is rejected at the door, so it never becomes a recipient your app fires transactional mail at - this is the highest-leverage place to catch it.
Verify any batch before an API or SMTP send
Before a bulk or triggered send, run the recipient list through Qualisend - upload a file to bulk cleaning (up to 1,000,000 addresses per job, duplicates charged once) or loop it through the API. The free plan's 100 one-time credits, which never expire, cover a first sample.
Read the results
Every address returns deliverable, risky, undeliverable, or unknown with a reason code, a 0-100 score, and sub-flags (catch-all, disposable, role, full mailbox), plus the MX provider and probe detail as evidence.
Suppress the failures on your side
Add every undeliverable to your own do-not-send list in your app or database - that's what actually keeps it out of the Send API, since Mailjet's Campaign Exclusion List only stops marketing mail, not transactional. Add them to the Campaign Exclusion List too if they also sit in a marketing or automation audience. Suppress on your side and the address never reaches a send, so Mailjet's 90-day block never has to fire.
Or automate it at signup
The highest-leverage option is to verify at the point of capture with the Qualisend REST API - scoped keys, rate limits, and webhooks - so a bad address is caught before your app ever stores it or fires a transactional message at it. No developer time to spare? Wire the same check through Zapier, Make, or n8n so new signups are verified before they're written to your database or synced to Mailjet.
What Qualisend flags on every address
- Never-verified invalid addresses that would hard-bounce on their first Send API delivery - before Mailjet's automatic block can fire
- Disposable / throwaway domains typed into your signup or checkout form
- Role addresses (info@, support@, billing@) that draw complaints on any marketing or automation stream
- Catch-all domains, flagged so you can hold back bulk mail and lean on the bounce webhook
- A 0-100 confidence score and machine-readable reason code for every address
The native Mailjet connector is live. Connect it in Qualisend under Integrations and work with your Mailjet list directly, no CSV needed.
What to do with each result
Every address comes back with a verdict and sub-flags. Here's the action that keeps your Mailjet list clean without throwing away contacts you can still reach.
deliverableSend through the Send API as normal.deliverable + role flagFine for transactional and system mail (info@, billing@); keep out of any marketing campaign or automation.risky + catch-all flagSend only high-value transactional mail and watch the bounce webhook; hold back bulk and marketing.risky + disposable flagAdd to your do-not-send list - the mailbox was built to expire, and a send to it is wasted.unknownRetry-safe - keep it and re-verify next batch; usually greylisting or rate-limiting, not a verdict on the mailbox.undeliverableAdd to your app's do-not-send list before it reaches the Send API; don't wait for Mailjet's 90-day block to fire after the bounce.Related reading
Verification is half of deliverability - authenticate your Mailjet sending domain too.
Verify at the point of capture and before every Send API call.
Spot-check a handful of addresses free before you wire up the API.
Why a first-send hard bounce costs a transactional sender more than a wasted send.
The bounce rate that makes Mailjet throttle or block your sending.
The 2024 bounce and complaint thresholds your Mailjet sends are judged against.
Mailjet verification FAQ
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