The 250ok Advantage

From stronger coverage to a best-practice approach to seed testing, you gain an advantage when using 250ok Inbox.

Optimized Seed Testing

Seedlist Optimizer (patent pending) enables you to weigh your results based on the composition of your email lists. Stop testing providers you don't mail to.

Learn more about Seedlist Optimizer

Automated Monitoring & Alerts

Live outside the app with custom email, SMS, Slack, HipChat, PagerDuty, and webhook alerts. Set it and forget it. Focus on what matters to you, free of pointless notifications.

Learn more about 250ok Alerts



Comprehensive Coverage

Enjoy 250ok's unparalleled coverage of B2B and B2C mailbox providers around the globe. Track your inbox placement and deliverability in real time to pinpoint and resolve issues.



Expert Services & Support

You won't find any junior-level script readers here. Ask for examples of deliverability issues 250ok diagnosed, triaged, and quickly resolved after other competitors failed.

Learn more about 250ok Services

Why use seedlist testing?

Seedlist testing reveals if your mail is passing global filters at Gmail, Microsoft, Yahoo/AOL, and all other providers.

When sending commercial email, it's important to understand what's likely to happen the next time you send to a recipient at a particular mailbox provider. Are your messages hitting SPAM at Yahoo! or going missing at Comcast? Are you sacrificing ROI because you lack the proper visibility into performance? Seedlist-based inbox monitoring is a key data point in solving this issue.

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Do you need email certification and panel data?

Old-school solutions to modern challenges are not a recipe for success. That's why we love debunking sender mythology — so you don't get burned.


Myth #1: Everyone Needs Email Panel Data!

No, everyone sending commercial email today already owns the most relevant panel in the world: the people they're sending mail to. With currently available panel offerings there is no statistical significance for most senders and the data is often misleading and hazardous given its severe biases.

Myth #2: Email Certification is a Smart Investment!

For most senders – not all – the juice is no longer worth the squeeze. Cert won't help you at Gmail, the largest mailbox provider in the world. Based on changes in the modern email landscape, 250ok customers combine best practices with expert services to achieve world-class performance.

Myth #3: Seedlist-based Inbox Testing is Dead!

While some vendors downplay the value of seedlist testing, do so at your own peril. Seeds are like spam traps: by the time the red flag goes up, there's already a problem. They are a critical component in testing perimeter defenses like blacklists, global spam filters, and reputation in general.

Resources for #SeriousSenders


More than 90% of US and UK nonprofits and their email recipients are highly susceptible to fraud.

The latest installment in 250ok’s Domain-based Message Authentication, Reporting & Conformance (DMARC) adoption reports brings us some truly shocking and disturbing findings: Nearly 95% of US-based nonprofit organizations (NPOs) have no DMARC policy to protect their email recipients from fraud. We also analyzed UK-based NPOs and found they fared only marginally better, with almost 93% […]

Free your July 4th marketing emails from bad design!

We want YOU to send better marketing emails for your Fourth of July sales. Why? Because what’s more American than driving holiday revenue? Thus, we are back again with more help from MailCharts to bring you a 2017 look-back to inform your 2018 campaigns. Together we looked at 1007 emails mentioning variants of “July 4th” […]

The new email authentication frontier: Brand Indicators for Message Identification (BIMI).

Over the last decade or so, marketers have been hard at work implementing Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM), and many have started down the road of implementing Domain-based Message Authentication, Reporting and Conformance (DMARC). But we never sleep on email, so we’re excited by the prospect of an additional frontier of […]




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