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 Experts

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


How has DMARC adoption evolved since 2018? It’s…complicated.

Guess who’s back, back again? It’s Matthew Vernhout, director of privacy at 250ok, with an all-new DMARC report for 2019! Tell a friend. Yes, this year we’re looking at how DMARC adoption rates fluctuated between our first glance at them in 2018 for a number of industries as well as taking a peek at different […]

Email Mythbusters: If my list is opt-in, I should get zero complaints.

At this point, we sound like a broken record but we’re 250ok with that. We think confirmed opt-in, or double opt-in, practice is the most basic standard for marketers to implement. If you’re asking someone to take an action to confirm their interest, and they do it, you can be relatively sure they’re in this […]

What we know about the Google Postmaster Tools outage.

**Update, 6/26: It looks like GPT is back up and running!** Daily senders all over the world look at their email statistics according to how Google and Gmail users view their performance. From complaints to reputation data, these numbers are calculated and shared by Google with marketers through Google Postmaster Tools. However, on June 13, […]




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