Mailjet is a popular choice for teams that want transactional and marketing email under one roof, with a friendly editor and a generous free tier. That accessibility pulls in a lot of fast-growing senders, and it also means Mailjet has to police reputation carefully to keep its shared infrastructure clean. If your bounce rate climbs too high, Mailjet does not look the other way. It throttles your throughput, flags your account for review, and can block sending entirely until you fix the underlying list.
The single biggest driver of a high Mailjet bounce rate is a dirty contact list. This guide breaks down the thresholds Mailjet watches, why bounces do so much damage, and the exact workflow to clean your list before every send so you never trip a sending block.
Why Mailjet Watches Your Bounce Rate
Every message you send through Mailjet rides on a shared reputation with the wider platform when you use shared IPs, and on your own reputation when you run a dedicated IP. A rising bounce rate tells mailbox providers like Gmail, Outlook, and Yahoo that you are mailing an unmaintained list, which is the classic fingerprint of a spammer.
Mailjet protects itself and its other customers by reacting quickly:
- Throughput throttling. Cross a bounce threshold and Mailjet can slow how fast your messages actually leave the queue, so a time-sensitive campaign drips out instead of landing.
- Account review and sending blocks. A sustained spike can pause your sending pending a compliance review, cutting off transactional and marketing email at the same time.
- Automatic suppression. Mailjet adds hard-bounced addresses to an exclusion list so they cannot be mailed again, which quietly shrinks your reachable audience every time you send dirty.
A bounce is not a neutral event. It compounds against your reputation, and it is almost always preventable at the list level.
The Bounce Rates Mailjet Expects You to Hold
Mailjet does not publish one hard cutoff for every account, but its deliverability guidance and industry norms point to clear lines you should not cross:
- Bounce rate under 5 percent. This is the widely referenced ceiling. Sustained bounce rates above roughly 5 percent put you in review territory.
- Spam complaint rate under 0.1 percent. One complaint per thousand delivered messages is the Gmail and Yahoo standard, and Mailjet holds you to it.
- Healthy target below 2 percent bounces. Strong senders keep hard bounces well under 2 percent. Treat anything above that as a warning sign, not an acceptable baseline.
The critical detail: Mailjet separates hard bounces (permanent failures like a nonexistent mailbox) from soft bounces (temporary issues like a full inbox). Hard bounces are the ones that destroy reputation and trigger suppression, and they are exactly the ones a clean list eliminates.
Why Your Mailjet List Goes Bad in the First Place
Even a list that was clean six months ago decays. The usual culprits:
- Natural churn. People change jobs and abandon addresses. B2B email data degrades by roughly 20 to 30 percent a year.
- Typos at capture. Signup forms collect
gmial.comandyahooo.comaddresses that hard bounce on the first send. - Purchased or scraped lists. These are riddled with dead mailboxes and spam traps, and they are the fastest route to a Mailjet sending block.
- Catch-all domains. Many business domains accept every address at the server, so standard verification tools return an ambiguous “unknown” and you send blind.
That last category is the one most teams get wrong, and it is where bounce rates hide.
The Catch-All Blind Spot Most Tools Ignore
Standard email verifiers connect to the recipient mail server and ask whether a mailbox exists. On a catch-all domain the server says “yes” to everything, so ordinary tools mark those addresses as unknown or risky and hand the decision back to you. Depending on your industry, catch-all addresses can make up 20 to 40 percent of a B2B list.
Faced with a pile of unknowns, teams do one of two harmful things: delete them all and throw away real, reachable customers, or send to all of them and eat the bounces that get their Mailjet account throttled or blocked.
This is precisely the gap Scrubby was built to close. Instead of giving up on catch-all and risky addresses, Scrubby uses a deeper validation process to determine whether the specific mailbox behind a catch-all domain is genuinely deliverable. You recover the reachable contacts other tools discard and drop only the addresses that would actually bounce, which is the difference between protecting your reputation and shrinking your reach.
A Step-by-Step Workflow to Cut Your Mailjet Bounce Rate
Follow this sequence before every meaningful send.
1. Export the contact list you plan to mail
Pull the exact contacts for the upcoming campaign from Mailjet, not your entire database. Validating the specific segment keeps costs down and gives you an accurate risk picture for that send.
2. Validate and resolve catch-all addresses
Run the list through a validator that handles catch-all and risky addresses rather than punting on them. Standard clean addresses pass, dead mailboxes get removed, and the ambiguous catch-all contacts get a real deliverable-or-not verdict. Using Scrubby here is what turns a wall of “unknown” results into confident keep-or-drop decisions.
3. Suppress hard bounces and complainers permanently
Keep Mailjet’s exclusion list synced with your source of truth so hard bounces and spam complainers never re-enter a send. Reintroducing a known bad address is one of the fastest ways to relight a reputation fire.
4. Segment by engagement before you press send
Prioritize contacts who have opened or clicked recently. If you must email a cold segment, warm up gradually rather than blasting the whole list in one shot, which spikes bounces and complaints together.
5. Rebuild the habit at capture
Add real-time validation to your signup and lead forms so typo and disposable addresses are caught the moment they are entered. Cold outreach teams booking meetings through tools like Kali benefit from the same discipline: a validated address list means invites and follow-ups actually land instead of bouncing before the prospect ever sees them.
Keep It Clean, Not Just Clean Once
A single scrub before a big campaign helps, but bounce rates creep back as lists age. Build validation into your routine:
- Re-validate any segment that has not been mailed in 90 days.
- Clean imported or purchased lists before they ever touch Mailjet.
- Watch your bounce and complaint stats in the Mailjet reporting dashboard after every send, and treat any upward trend as a prompt to re-clean.
Mailjet gives you the sending infrastructure, but it holds you responsible for who you send to. Keep your hard bounces low, resolve the catch-all addresses instead of guessing, and you protect both your sender reputation and your ability to keep sending at all. Validating your list with Scrubby before each campaign is the simplest insurance against a throttled or blocked Mailjet account.
Abhinav
Content Writer