Mailjet deliverability: domain setup, IP choice and what to watch

Mailjet, part of Sinch's email group alongside Mailgun, sends from shared IP pools on most plans, with dedicated IPs available higher up. That one fact determines your deliverability strategy: the IP reputation is not yours to manage, so the asset you control is your sending domain. Authenticate it properly, keep your list clean, separate your streams, and measure folder placement — because Mailjet's delivery statistics count acceptances, and a message filed in Junk is an accepted message.

Authenticate the sending domain

In Mailjet's sender-domain settings you authenticate a domain rather than individual addresses, which gives you SPF and DKIM records to publish.

example.com.                  TXT   "v=spf1 include:spf.mailjet.com ~all"
mailjet._domainkey.example.com TXT  "k=rsa; p=MIGfMA0GCSqGSIb3DQ..."
_dmarc.example.com.           TXT   "v=DMARC1; p=none; rua=mailto:dmarc@example.com"

Take the exact record values from your own account rather than from any article, including this one — selectors and include hosts change. Then verify the things dashboards do not check:

1. One SPF record only. Two v=spf1 records is a permanent failure, not a merge. If you already send through other platforms, add the include: to the existing record.
2. Under ten DNS lookups. Each include: costs lookups and the cumulative total is capped at ten; exceeding it yields a permerror and SPF stops protecting you.
3. DKIM alignment. Send yourself a message and read Authentication-Results: you want dkim=pass with the signing d= on your own domain, because a pass on the platform's domain does nothing for DMARC.
4. Custom return path / bounce domain where your plan supports it, so SPF aligns as well as passes.
5. A tracking domain on your own subdomain rather than a shared one, since link domains carry their own reputation independently of yours.

Shared pool or dedicated IP

The decision rule that holds: if you cannot send meaningfully every single day, including quiet weeks, stay in the shared pool. A dedicated IP that goes quiet performs worse than a well-run pool. If you do take one, ramp it slowly, splitting each day's volume across providers in your list's proportions, and let deferrals set the pace — a persistent 421 4.7.0 from one provider means hold that provider flat.

Separate your streams

Do not send transactional mail, newsletters and outbound from one domain. Use subdomains so one stream's complaint rate cannot filter another, and keep the root domain for mail people expect.

• mail.example.com — receipts, resets, notifications
• news.example.com — marketing, with one-click unsubscribe
• a separate sending domain entirely for cold outreach

Watch the right signals

Mailjet's statistics give you sends, bounces, opens, clicks and complaint events, and the bounce and complaint numbers are the ones worth acting on. Keep hard bounces under 1% and treat 2% as a stop-and-clean threshold; Mailjet, like every platform, suppresses hard bounces and will act on sustained abuse of its shared pools.

Alongside that, use the signals the platform cannot see for you:

• Gmail spam rate in Postmaster Tools, under 0.3% and ideally under 0.1%. Note the domain and IP reputation charts there are retired, so there is no reputation grade to track.
• Per-provider seed placement from mailboxes you control. This is the only way to catch a Microsoft 365 block, which arrives as accepted-then-quarantined and shows as success in your platform stats.
• Blocklist state for your domain, your link domains, and the IP if you have a dedicated one.
• Open-rate caveats. Apple Mail Privacy Protection pre-fetches images, so opens are partly machine traffic; use clicks and replies, with sub-second datacentre clicks filtered out.

One Gmail measurement note: the Promotions tab carries the INBOX label, so any placement number derived from reading labels counts a Promotions landing as a clean inbox hit.

What not to do

Do not treat Mailjet's delivery rate as deliverability — it counts 250 OK. Do not import a purchased or unverified list; on a shared pool that affects other tenants and platforms enforce against it. Do not send your first campaign at full volume from a newly authenticated domain; ramp the domain even though the IP is warm. Do not point your tracking links at a shared shortener. Do not leave DMARC at p=none forever — read the aggregate reports, then move to quarantine and reject. And do not switch platforms to escape a deliverability problem: domain reputation follows you, so unless the cause was genuinely a pool, you will take the problem with you.

On warm-up specifically, ramp real mail to real recipients. Pools of controlled mailboxes manufacturing opens, clicks and replies are what Validity's Heatwave blocklist, launched 3 September 2026, targets; it lists domains rather than IPs, launched with over a million listed, and publishes no thresholds, so no tool including ours can promise exemption.

MailPilot works alongside a platform like Mailjet rather than replacing it: it warms mailboxes over OAuth or SMTP/IMAP including custom SMTP relays, validates SPF, DKIM and DMARC on your sending domains, measures real per-provider inbox placement through a seed network, and records per-mailbox reputation daily.