MailAdx vs Kevel for email ad serving
Kevel is an API-first ad server for engineering teams. MailAdx is a purpose-built platform for newsletter operators. Here's how to choose.
Kevel (formerly Adzerk) is a powerful ad serving API designed for engineering teams that want to build custom ad experiences. It exposes a low-level API with no opinionated UI — you bring the frontend, the business logic, and the integrations. It's the right choice when your product is software and the ad experience is deeply embedded in your application.
MailAdx takes the opposite approach: a complete platform for newsletter operators, with a publisher portal, advertiser DSP, and open-time ad server that works without writing a single line of custom code. Paste the ad tag in your ESP template; the waterfall runs automatically at open time.
The choice usually comes down to whether you have dedicated engineering resources and need maximum flexibility (Kevel), or whether you want a newsletter-specific platform that's live in an afternoon without a software project (MailAdx).
Kevel's pricing is calibrated for software products that run millions of ad decisions per month — SaaS applications, marketplaces, classified sites, and developer-built ad networks. The API call model makes sense at that scale. For newsletter publishers whose monthly impression volume is measured in tens of thousands rather than millions, Kevel's pricing tier and the engineering investment to configure it can easily exceed the annual ad revenue the newsletter generates.
The email-specific engineering required on Kevel is worth spelling out in detail. Gmail's image proxy caches remote images and must be bypassed with a nonce or unique URL parameter to ensure each open triggers a fresh ad auction rather than returning a cached creative. Apple Mail Privacy Protection pre-fetches remote images when an email arrives, which inflates open counts unless you account for MPP bot opens differently. Composite PNG native ads require a server-side image compositor. Building those three capabilities on top of Kevel's API is a multi-week engineering project. MailAdx handles all three out of the box.
Publishers sometimes ask whether MailAdx has a public API. It does: placements, campaigns, creatives, and reporting are all accessible via REST. The difference from Kevel is that MailAdx ships a fully functional platform on top of its API — you can use it without touching code, or use the API to extend it. Kevel ships the API and expects you to build the platform on top.
Feature comparison
| Feature | MailAdx | Kevel |
|---|---|---|
| Built for email newsletters | ||
| Zero-code publisher setup | ||
| Open-time ad decisioning | ||
| Publisher portal (no code required) | ||
| Advertiser self-serve DSP | ||
| API-first architecture | ||
| Custom ad experience (any surface) | ||
| Native ad format (composite PNG) | ||
| Gmail proxy + Apple MPP handling | ||
| OpenRTB integration | ||
| Multi-tenant network support | ||
| Ad Journeys (sequential campaigns) | ||
| Self-serve onboarding | ||
| Web / app / CTV inventory support |
Where MailAdx wins
Platform vs toolkit
Kevel gives you a set of primitives and an API; building a working ad server still requires significant engineering investment. MailAdx is a complete platform — publisher portal, advertiser DSP, reporting, and billing are all shipped and maintained. Most newsletter operators are live within hours, not months.
Email-specific handling built in
MailAdx handles the quirks of email advertising that a generic ad API doesn't: Gmail image proxy nonce bypass for fresh auctions, Apple Mail Privacy Protection labeling, open-rate denominator correction, and composite PNG native ads that render without JavaScript. With Kevel, building these requires custom engineering.
Advertiser self-serve included
MailAdx includes a full advertiser DSP — advertisers can self-serve campaigns, upload creatives, and access delivery reports without publisher involvement. Kevel is publisher-side only; you'd need to build an advertiser-facing product separately.
Pricing for newsletter scale
Kevel's pricing is designed for high-volume software products. MailAdx's plans are designed for newsletter operators, with per-impression pricing that scales naturally with your send volume.
When Kevel is the better choice
- You have dedicated backend engineers who want full API control over ad decisioning logic.
- Your ad surface isn't email — Kevel serves ads in web apps, mobile apps, and custom digital products natively.
- You're building a multi-channel ad server (web + email + app) and need one API across all surfaces.
- You need to embed ad logic inside your own SaaS product and want a headless API, not a separate platform.
Not sure which fits your situation? Talk to us — we'll give you an honest recommendation.
Frequently asked questions
Is MailAdx an alternative to Kevel for newsletter publishers?
Yes. Kevel is an API-first toolkit that requires engineering to build a working ad server. MailAdx is a complete newsletter ad platform — publisher portal, advertiser DSP, and open-time serving — that works without writing code. If your newsletter is your product, not a software application, MailAdx is almost always the faster, cheaper path to ad revenue.
Can Kevel handle open-time email ad serving?
Kevel can serve ads via dynamic image URLs, which is how open-time email serving works technically. But Gmail proxy bypass, Apple MPP handling, open-rate denominator correction, and composite PNG native ads all require custom engineering on top of the base API. MailAdx handles these natively — they're built into the serving layer, not left to you to implement.
How much engineering does Kevel require compared to MailAdx?
A basic Kevel integration for email requires building a decision endpoint, an ad tag generator, a publisher-facing reporting dashboard, and handling email-specific quirks. Estimate 4–8 engineering weeks minimum for a production-ready setup. MailAdx setup for most ESPs takes 30–60 minutes: create an account, set up an ad unit, paste the tag, and test. No ongoing engineering maintenance required.
Which platform is better for a newsletter publishing company running multiple newsletters?
MailAdx supports multi-publisher network accounts where you can manage ad inventory, campaigns, and billing across many newsletters from one dashboard. Kevel also supports multi-tenant architectures, but you'd need to build the publisher-facing portal yourself. MailAdx ships that portal as part of the platform.
Does MailAdx have an API?
Yes. MailAdx's REST API covers placements, campaigns, creatives, delivery reports, and publisher management — useful for automating campaign uploads, syncing reporting data to internal systems, or building publisher-facing features on top. The API is an extension layer; the platform works fully without it.
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