Past Mailjet?
The Sinch consolidation is the story.

The product as it exists in 2026 has clear strengths and clear gaps, and the gaps have widened in the 2024-2026 window as Sinch's investment focus moved to other portfolio products. The strengths first. Mailjet's real-time template collaboration genuinely works — multiple team members can edit the same email template simultaneously, see each other's cursors, and resolve merge conflicts inline, in a Google-Docs-style experience that no other email platform offers in 2026. For design-led teams where the template authoring is a multi-person workflow (designer, copywriter, brand reviewer, legal reviewer), this feature meaningfully reduces email-production cycle time. We have heard direct feedback from prospects that this single feature has been the reason they stayed on Mailjet through the Sinch acquisition uncertainty.

EU data residency is the second clear strength. Mailjet was French-founded, its primary engineering and operations were Paris-based through the acquisitions, and the data centres serving European customers remain in France and adjacent EU regions. The platform's certifications — ISO 27001 and 27701, SOC 2, PCI DSS, GDPR, CCPA, HIPAA, plus Certified Sender Alliance membership — are extensive and well-documented. For procurement teams that need to clear an ESP through a security review, Mailjet's certification depth is usable directly rather than requiring negotiation. The DPA is straightforward and the sub-processor list is shorter than most US-origin competitors.

The gaps are where the Sinch consolidation has produced friction. Deliverability is the most-cited issue across independent reviews and customer reports in 2024-2026. EmailToolTester's January 2024 deliverability study placed Mailjet around 88.3% across the seedlist; subsequent quarterly measurements have varied between 84% and 91% depending on which receiver mix is dominant. The variability traces to Mailjet's heavy use of shared IP pools at the entry-level and mid-tier price points, combined with strict account-engagement monitoring that occasionally produces account-stability issues that customers report as opaque suspensions. Dedicated IPs are available but only on Premium plans and above, and at price points that compete unfavourably with single-purpose transactional providers.

The analytics are basic relative to dedicated infrastructure products. Standard delivery metrics (sent, delivered, bounced, opened, clicked) are present. Advanced metrics that operations teams rely on at scale — per-receiver bounce categorisation, time-series IP reputation, predictive deliverability scoring, automated reputation-recovery workflows — are either absent or rudimentary. For senders evaluating Mailjet at the 100K+ monthly volume level, the analytics layer becomes a meaningful constraint.

The strategic direction is the largest unstated gap. Sinch's portfolio strategy through 2024-2025 has emphasised the SMS and conversational-messaging products over the email products. Mailjet's roadmap in publicly-visible release notes shows incremental rather than ambitious development: AI subject-line suggestions, improved drag-and-drop editor, additional template categories. The features that would move Mailjet from competent middle-tier to category-leading — dedicated IP automation, advanced deliverability remediation, regulator-grade audit logging, native integrations with EU-specific compliance tooling — are absent from public roadmap commitments. The product is being maintained rather than developed.

Profile one: small-to-mid agencies and in-house creative teams where template collaboration is a workflow bottleneck. An e-commerce brand with a 5-person marketing team, sending weekly newsletters plus monthly campaigns, where the template authoring process involves a designer, a copywriter, a brand manager and a legal reviewer cycling through 3-4 revisions per template. Without real-time collaboration, this cycle takes 5-7 working days from brief to send-ready template. With Mailjet's collaboration, the same cycle compresses to 1-2 days. The deliverability variability is acceptable at this volume because the brand is not running mission-critical transactional traffic. The Premium plan at $35-50/month is affordable. The Sinch ownership concerns matter less because the team is not investing in deep platform integration. This is Mailjet's natural home.

Profile two: French and European SMB senders with strict GDPR-first procurement requirements and sub-50K monthly volume. A French B2B SaaS at €500K-€2M ARR, sending product update emails plus transactional notifications, with a procurement process that requires EU data residency, French-language support, and a French-domiciled vendor for the local compliance posture. Mailjet's Paris origin, EU data centres, and French customer-support team match this requirement exactly. The pricing is competitive at sub-50K volume. The deliverability variability is acceptable because the sender's audience is predominantly French B2B inboxes which are less sensitive to shared-pool reputation than consumer Gmail/Yahoo populations.

Outside these two profiles, the Mailjet fit becomes harder to defend. The collaboration feature stops being a differentiator above 10-person marketing teams (which usually have dedicated marketing-ops engineers who script template management). The EU residency claim is matched by other EU-origin providers including Brevo and ourselves. The deliverability variability becomes binding for mission-critical transactional traffic. The strategic-direction uncertainty makes Mailjet a risky multi-year procurement bet for enterprise customers.

Volume above 100K monthly with deliverability sensitivity. Mailjet's shared-IP infrastructure handles volume below 100K well; above that, the shared-pool reputation variability starts producing observable inbox-placement degradation for senders with even slightly imperfect list hygiene. The Mailjet upgrade path is the Premium plan with a dedicated IP, but the dedicated-IP cost at Mailjet's pricing compares unfavourably with our managed SMTP Relay or KumoMTA service. Our pricing at 100K-500K monthly volume on dedicated IP is €249-€499/month with no per-message overage; Mailjet's equivalent runs $90-$200 for the email allocation plus dedicated-IP add-on at premium tier pricing. The cost converges; the deliverability does not — our dedicated-pool reputation management at this volume produces measurably better placement than Mailjet's mid-tier shared pools.

Transactional-critical workloads. Mailjet handles transactional adequately but is not optimised for it the way Postmark or our own SMTP Relay is. The shared infrastructure with marketing traffic means transactional deliverability is partially exposed to the marketing-send hygiene of other Mailjet customers in the same pool. For senders whose business model depends on transactional email landing in inbox — password resets that gate revenue, verification codes that gate sign-up conversion, receipts that affect customer-support load — the Mailjet shared-pool architecture is a known risk. Our infrastructure separates transactional from marketing traffic by design, and the dedicated IP for transactional traffic is included at the SMTP Relay Standard tier upward.

Strategic-direction-sensitive procurement. Enterprise procurement processes that require multi-year contractual commitments tend to weight the strategic direction of the vendor heavily. Sinch's portfolio strategy through 2024-2026 has visibly de-prioritised the email product line in favour of conversational messaging (SMS, WhatsApp, RCS). For an enterprise customer signing a 3-year Mailjet contract in 2026, the question of whether Mailjet will exist as a distinguishable product in 2029 is legitimate. Our business is single-product (managed email infrastructure), single-purpose, and operated by the same founding team since 2002. The strategic-direction question reduces to "are we still in business" rather than "is this product line still a priority within a larger portfolio." For procurement teams that have been burned by vendor strategic shifts in the last decade, this matters.

Regulated-sector EU senders. Mailjet's certifications (ISO 27001 plus ISO 27701 plus SOC 2 plus GDPR-compliant plus HIPAA-capable) cover the platform-level requirements of most regulated sectors. The gap appears at the operational level when a sector regulator audits the actual processing architecture: which sub-processors handle the workload, what the chain of custody for personal data is, what the residency commitment looks like under operational stress. Mailjet's documentation is competent; the practical answers to specific regulator questions tend to come back from Sinch's central security team rather than from a Mailjet-specific compliance owner, and the response timelines lengthen accordingly. Our compliance posture is single-product and the answers come back from named individuals (Mikael for technical compliance, [email protected] for data-protection questions, [email protected] for incident response). For regulated sectors where the audit trail matters, single-product transparency tends to clear faster.

Scenario A: 25K monthly email, marketing-led EU sender with template collaboration as a workflow priority. Mailjet Essential at $17 monthly = $204 annual. BIG BOX SMTP Relay Starter at €99 monthly = €1,188 annual. Mailjet wins clearly on cost and workflow fit. The collaboration feature alone justifies the choice for design-led teams. We will not push to compete in this band.

Scenario B: 200K monthly mixed (transactional + marketing), B2B SaaS, deliverability-sensitive. Mailjet Premium at approximately $70-90/month for the email allocation, plus dedicated IP add-on at $80-120/month = $150-210 monthly = $1,800-2,520 annual. BIG BOX SMTP Relay Sender at €259/month with dedicated IP included = €2,988 annual. Costs converge; deliverability gap favours BIG BOX. The 20-30% premium pays for the deliverability differential we model at this volume — our internal data shows 4-6 percentage points of inbox-placement improvement at this band against shared-pool Mailjet alternatives, which on a transactional-critical workload is worth multiples of the cost differential.

Scenario C: 1M monthly bulk marketing, e-commerce platform, EU-only. Mailjet Enterprise (custom pricing, typically $800-1,500 monthly at this band depending on negotiation) + multiple dedicated IPs = $1,200-2,000 monthly. BIG BOX managed KumoMTA dedicated at €1,299/month with full pool ownership = €15,588 annual. Costs comparable; control surface favours BIG BOX. At this volume the question is operational control — can the sender's deliverability team interact with the MTA configuration, traffic-shaping rules, and IP-rotation strategy. Mailjet's platform abstracts these decisions; our managed KumoMTA exposes them. For senders with internal deliverability expertise, the BIG BOX architecture is materially preferable.

The architectural choice is shared IP pools for the entry and mid-tier price points. Mailjet, like Brevo and SendGrid Essentials and Postmark's Basic plan, places customer traffic on IP pools shared with other Mailjet customers in the same tier. The pools are managed — Mailjet's deliverability team monitors aggregate complaint rates, blocks senders who exceed engagement thresholds, and rotates IPs out of pools where reputation deteriorates. The management is competent. The fundamental constraint remains: your inbox-placement reputation is partially determined by other senders in your pool.

The variability shows up in two patterns. The first is temporal: when one or more large senders in a Mailjet pool experience an engagement crash (a campaign that produces high spam complaints, a list-quality incident, a bounced-rate spike), the pool reputation degrades for hours-to-days before the offending sender is rotated out. During the degradation window, every sender in the pool sees inbox-placement drop. The drop is typically 3-8 percentage points; for mission-critical transactional traffic this is the difference between "verification code arrives in inbox" and "verification code goes to spam." The second pattern is steady-state: pools that are well-managed produce stable 88-91% inbox placement, but the absolute level is lower than dedicated-IP traffic from the same sender would produce. The 5-8 percentage point gap between shared-pool 88-91% and dedicated-IP 94-97% is the cost of pool architecture, not the cost of Mailjet specifically.

Mailjet's response to this constraint is the Premium-tier dedicated IP. This is the right answer architecturally but the implementation has friction: the dedicated IP requires a Premium plan upgrade ($35-50/month minimum), requires manual warmup that Mailjet does not automate as completely as PowerMTA or KumoMTA do, and is billed as an add-on rather than a default. Our approach is different: dedicated IPs are included in the SMTP Relay Sender tier (€259/month) at no add-on cost, the warmup is automated against published Microsoft and Google guidelines, and the underlying pool architecture is operationally separated between customers from the day one.

The honest framing: Mailjet's deliverability is fine for the workloads Mailjet is built for, which are mid-volume marketing-led senders with adequate list hygiene who can absorb occasional shared-pool reputation drops. It is meaningfully worse than dedicated-IP managed-MTA infrastructure for workloads where each percentage point of inbox placement maps directly to revenue.

Two practical examples from our 2025 engagement notes. A French e-commerce platform sending 180K monthly mixed (transactional plus marketing) reported a 4.2% revenue uplift in the 90 days after migrating from Mailjet shared pools to BIG BOX dedicated infrastructure. The uplift traced directly to a 6.1 percentage point inbox-placement improvement on transactional receipts and order confirmations. The revenue model: customers who receive order confirmations promptly are measurably more likely to complete repeat purchases within the next 14 days. A second example, a German B2B SaaS at 80K monthly transactional volume, measured a 14% reduction in support tickets after the same migration. The mechanism: verification emails landing in inbox rather than spam reduced the new-user onboarding support load. These specific numbers will not generalise to every migration; the order of magnitude (single-digit percentage revenue impact, double-digit percentage support-load impact) is consistent with what we see across the customer base.

Sinch acquired Mailgun in November 2021 for $2.85B and Mailjet via the Mailgun acquisition (Mailgun had acquired Mailjet in 2019 for $42M). Sinch positioned both products as part of a unified "Customer Communications Cloud" alongside its SMS plus voice plus conversational-messaging products. The unified positioning has not produced unified product development: Mailgun and Mailjet continue to operate as separate products with separate APIs, separate billing systems, separate documentation, and separate (overlapping) target customer profiles.

Sinch's reported revenue for 2024 placed conversational messaging (SMS, WhatsApp, RCS) at approximately 78% of total revenue and email products at approximately 14%, with the remainder distributed across voice plus identity plus several smaller product lines. The 14% figure compares against an estimated industry revenue of $4.2B across the email-API category in 2024, meaning Sinch's email products combined are a single-digit percentage of the overall market. The strategic-attention argument follows from these numbers: a 14% revenue line within a larger portfolio receives proportional engineering investment, which in Sinch's 2024-2025 public capital allocation showed up as below-portfolio-average headcount growth on the email products.

Mailjet's specific 2024-2026 release notes show maintenance work — security patches, regulatory compliance updates, drag-and-drop editor improvements, integration partner additions — without the headline feature releases that would signal strategic priority. The collaboration feature was released in 2018, pre-Sinch. The AI subject-line generator was released in 2023 as a small feature. There has been no major architectural release since the Sinch acquisition.

This does not mean Mailjet is going to be deprecated. Sinch has explicitly committed to maintaining both Mailgun and Mailjet as separate products. It does mean that customers signing 3-year procurement commitments on Mailjet in 2026 should expect a 3-year product trajectory that matches what they see today, not the trajectory they might have expected from pre-Sinch Mailjet circa 2018. For procurement teams comparing Mailjet to dedicated managed-MTA infrastructure on a multi-year horizon, the strategic-direction question is real and we surface it openly.

The technical migration follows the same five-phase parallel-sending pattern we use for SendGrid migrations and for Postmark transitions. Phase 1 provisions DKIM keys, updates SPF to include both Mailjet's spf.mailjet.com and our spf.bigboxhosting.com in parallel, preserves DMARC alignment. Phase 2 routes 10% of traffic through BIG BOX while 90% continues through Mailjet. Phase 3 scales to 50%-70%. Phase 4 cuts over to 100% BIG BOX. Phase 5 decommissions the Mailjet account.

The Mailjet-specific complications are template migration and suppression-list reconciliation. The template migration matters because Mailjet's collaboration feature has typically produced more templates over the platform's life than the customer realises — we have seen accounts with 200-400 templates accumulated over years, many of them obsolete. The migration is an opportunity to audit. The opportunity extends to deduplication. It then extends to rebuilding the template library on our infrastructure (which does not offer the same collaboration UX, which is the trade-off the customer chose when migrating). The suppression-list reconciliation is mechanical: Mailjet's API exports the list, we import to our infrastructure, ongoing bounces and unsubscribes are mirrored during the parallel-sending window.

The commercial complication is Mailjet's contract structure. Most Mailjet customers are on monthly plans, which means cancellation is straightforward. Enterprise tier customers on annual or multi-year contracts have the same options as Bird/Sparkpost customers: ride out the current contract with parallel infrastructure on BIG BOX, negotiate volume reduction with Mailjet's account team, or accept the lock-in cost. Our experience has been that Mailjet's account teams accommodate volume reduction reasonably; the company is competent at customer retention but not aggressive about contract enforcement.

Question one: is real-time template collaboration a workflow priority that you cannot reproduce with a separate tool? If yes, Mailjet is the answer for this workflow. The collaboration feature is genuinely best-in-category and we cannot match it.

Question two: is your monthly volume below 50K, your traffic mix marketing-led, and your deliverability tolerance moderate? If yes, Mailjet remains a defensible choice. The pricing is competitive at this band and the deliverability variability is absorbable for most marketing workloads.

Question three: is your volume above 100K, your traffic transactional-critical, or your procurement multi-year and strategic-direction-sensitive? If yes, BIG BOX. The deliverability advantage of dedicated-IP managed infrastructure becomes binding at this band, and the strategic-direction risk of betting multi-year on a Sinch portfolio member is real.

The conversation we recommend is a 30-minute scoping call with an engineer who has run Mailjet migrations. We will model your specific cost and deliverability profile and tell you whether the migration math works. If Mailjet remains the right answer for your shape, we will say so.