What's new on mailfloss

Who’s affected: anyone generating new mailfloss API keys.

New API keys are now issued exclusively in the secure mf_live_ format, stored hashed at rest — the old plaintext key format can no longer be generated. Existing legacy keys keep working, so nothing breaks today.

What to do: when convenient, create a new key from your dashboard’s API settings and swap it into your integration. We’ll give plenty of notice before legacy keys are retired entirely.

Connecting ClickFunnels to mailfloss is now a guided two-step flow: enter your API key, then pick exactly which team and workspace you want mailfloss to clean. No more guessing which workspace a key belongs to — you see your options and choose.

If you connected ClickFunnels before and had trouble, try reconnecting — the new flow sorts it out.

We audited every one of our email service provider integrations end to end and shipped fixes across more than 40 of them — HubSpot, Klaviyo, Mailchimp, ActiveCampaign, ConvertKit, Constant Contact, AWeber, Brevo, Beehiiv, and many more.

What you’ll notice: imports that previously could stall partway now run to completion, large lists page through reliably, typo fixes apply more accurately, and connection problems surface clearly instead of failing silently. If an integration ever felt flaky, it should feel noticeably more solid now.

You can now create, list, update, and delete webhook subscriptions directly through the mailfloss API — no dashboard visit needed. Point a subscription at your endpoint, choose the events you care about, and mailfloss notifies your systems the moment verifications finish.

Each subscription comes with a signing secret so you can verify that events really came from us. See the developer docs to get started.

The mailfloss website got a complete redesign — a cleaner look, a new brand, and pages that finally do a good job of explaining what mailfloss actually does for your list. Whether you are here to see how automatic email cleaning works, compare plans, or read up on a specific integration, everything is easier to find and quicker to read.

This is the first step of a bigger refresh. The same care is now coming to the dashboard you use every day, so the app you log into feels as sharp as the new site. More on that soon.

Nothing about your account, your connected platforms, or your cleaning schedule changes — same mailfloss, just a much nicer front door.

The mailfloss v1 API is now our recommended way to build on mailfloss. It uses modern Authorization: Bearer authentication, predictable resource-based endpoints, and clearer errors, pagination, and rate-limit headers — all covered by the interactive reference at developers.mailfloss.com.

Already building on the legacy API? Nothing breaks today — it stays fully supported until it sunsets on June 1, 2027, and moving over is usually a small change (swap a ?api_key= query parameter for an Authorization: Bearer header). Each legacy docs page links straight to its v1 replacement.

Your dashboard’s results table now keeps verified email addresses hidden by default — you see the verdicts (passed, reason, status) without contact data on screen. Click “View email addresses” whenever you want to show them. A more private dashboard, by default.

The full docs for the mailfloss v1 API are now live at developers.mailfloss.com. The centerpiece is an interactive reference: browse every v1 endpoint, see the exact request and response for each one, and try real calls right from the page. Because it is generated straight from the API, it stays in sync with the endpoints, so you build against what they actually do and catch problems before you ship.

There are also short guides for the parts people get stuck on: getting started, authentication, errors, pagination, rate limits, and connecting your email platform.

Already building on the legacy API? Nothing changes for you right now. It is still fully documented, now clearly marked as legacy, and it sunsets on June 1, 2027. Moving to v1 is a small change in most cases (swapping an ?api_key= query parameter for an Authorization: Bearer header), each legacy page links straight to its v1 replacement, and the quickstart is the best place to start.

You can now upload Excel spreadsheets in the file uploader, in the same place you upload CSV files. Supported formats are .xlsx, .xls, .xlsb, .xlsm, and .ods. Your spreadsheet is converted and processed just like a CSV upload, and your original file stays available for download.

A couple of things to know: we read the first worksheet of a multi-sheet workbook, and your file should have a header row, the same as a CSV.

There’s a bonus, too: the free Append results option now works for Excel uploads, not just CSVs. Switch it on before you export and we’ll add your email verification results — a status and reason for each address — back into your original spreadsheet.

Because Excel upload is now built in, we’ve removed the old standalone “Upload a spreadsheet” tool. We’ve also retired the “Import address book” option. If you previously imported contacts from an address book, you can export them to a spreadsheet or CSV and upload the file, or paste your addresses directly.

Open the file uploader →

If your team uses our legacy API endpoints, here’s an important heads-up: we’re retiring them, and you’ll need to move to our current API before they’re switched off.

Deadline: June 1, 2027. After that date, the legacy endpoints will stop responding.

Does this affect you? Only if you call the legacy API directly from your own code or scripts. If you use our native integrations (Mailchimp, Klaviyo, HubSpot, GoHighLevel, and the rest) or Zapier, you’re all set — nothing changes for you.

What’s next: we’re putting the finishing touches on our current API and a full migration guide. We’ll post it right here in the changelog — and email it to you — as soon as it’s ready, well ahead of the deadline.

There’s plenty of runway, and we’re here to help. If you call the legacy API directly and want to get ahead of the migration, reach out to support any time.

We also sent this to your inbox earlier this week — this post is here so it’s easy to find and link back to.

If you’re connected to multiple integrations, you know the pain: a few report emails land in your inbox, and you have to open each one to figure out which integration it’s for.

Not anymore. Report emails now include the integration name right in the subject line.

So instead of:

“Your emails are flossed”

You’ll see:

“Your emails are flossed for Klaviyo (Main Store)”

Quick to scan, easy to sort, no more guessing.

This is especially useful if you’re managing multiple accounts or running different lists across different ESPs.

No action needed on your end. This is already live for all accounts. 🚀

GoHighLevel is an all-in-one marketing platform trusted by agencies and marketers to build funnels, automate workflows, and scale client results. And now, with mailfloss baked right into your GoHighLevel setup, keeping your email lists clean and performing at their best is easier than ever.

With the mailfloss + GoHighLevel integration, you get:

✅ Instant email verification the moment contacts are added
🛠 Real-time typo correction so you don’t lose leads to simple mistakes
🔄 Automated list cleaning—unsubscribe, delete, or update custom fields of bad emails
📬 Lower bounce rates and stronger inbox placement
💡 Improved sender reputation and campaign ROI with zero manual effort

Want to start sending smarter?
Just head to Integrations in your mailfloss dashboard and hit Add Integration to link your GoHighLevel account.

Less list anxiety, more results—this one’s for every agency and marketer who’s tired of wrestling with bad data. Go get it!

Say goodbye to email bounces—right from Airtable. With the new mailfloss Email Verifier extension, you can now clean your email lists without ever leaving your base.

✅ Verify emails directly in Airtable
⚡ Instantly check thousands of records
🔍 Identify invalid, risky, and typo-ridden addresses in seconds

Ready to protect your sender reputation and boost deliverability?

👉 Install the extension here

Encharge is a powerful marketing automation platform built to help you convert more leads, nurture customer relationships, and drive revenue—without the manual grind. And now, with mailfloss seamlessly integrated into your Encharge workflow, you can keep your email lists clean and conversion-ready—automatically.

With the mailfloss + Encharge integration, you’ll unlock:

✅ Real-time email verification at the point of capture
✍️ Automatic typo correction to save missed leads
🔁 Ongoing list cleaning and hygiene to protect sender reputation
📉 Reduced bounce rates and improved inbox placement
🚀 More efficient automations and higher email ROI

Ready to clean up your list and power up your automations? Head to Integrations in your mailfloss dashboard and click Add Integration to connect your Encharge account today.

We can’t wait to see how this new integration helps you maximize your campaign performance and simplify your workflow.

Tired of bouncing emails messing up your campaigns? Now you can verify email addresses directly inside Google Sheets with the mailfloss Email Verifier extension—no more switching tabs or manual work!

✅ Verify emails without leaving your spreadsheet
⚡ Process thousands of emails in seconds
🔍 Instantly filter out bad addresses

💡 Ready to clean up your email lists? Install the mailfloss Google Sheets extension today and say goodbye to bad emails!

🔗 Install Now

Beehiiv is a powerful email marketing platform designed specifically for creators and publishers. Our new integration brings Instafloss’s real-time email verification directly into your beehiiv workflow, ensuring your email lists stay clean, accurate, and high-performing.

With the mailfloss beehiiv integration, you’ll get:

Instant email verification at the point of entry
Automatic typo correction
Automated unsubscribe, delete, and/or labels updating
Reduced bounce rates and improved email deliverability

Ready to supercharge your email list? Navigate to Integrations and click the Add Integration button to connect your beehiiv account and start optimizing your email list quality today. We can’t wait to hear how this integration helps streamline your email marketing efforts!

Our Click Funnels email verification integration is now available. Click Funnels is a powerful sales funnel builder that helps entrepreneurs turn visitors into customers. And with our integration, you get Instafloss real-time email verification, an automated typo-fixer, automated custom field updating, deleting, and more.

Feel free to connect your Click Funnels account by visiting Integrations and clicking on the Add Integration button to get started. We’re excited to hear your thoughts on the integration.

We’ve released a new API for our Integration Settings. The API is in beta and we are actively seeking feedback.

Right now you are able to add blacklist and whitelist options to any integration using this API - both in bulk and one at a time. We will add additional endpoints in the future based on your feedback. Please give it a try and let us know what you think.

API documentation is available at including an overview, reference, and examples - https://developers.mailfloss.com/integration-settings-api-overview

We’re happy to announce we’ve now added support for Single Sign On using SAML or OIDC.

Please reach out if your organization uses either SAML or OIDC and you’d like to test it out.

This feature will be available on premium plans or as an add-on, but will be included for free for anybody willing to help us test it out.

We’re happy to announce that our Zapier integration is out of beta. It no longer requires an invite to use and can be found within the Zapier marketplace.

You can also find it directly in the mailfloss app by going to Plugins and selecting Zapier. Direct link here.

Happy Zapping!

We’ve added the ability to register an account and log in using Azure AD authentication. No password is needed so this is generally a more secure method of logging in.

Azure AD Authentication works for personal Outlook addresses as well as Microsoft Azure AD business accounts.

If you already have an account registered with the same email address, the first time you try to log in using this method will link this authentication method with the account. And subsequent login attempts will succeed.

Give it a try and let us know what you think.

We’ve added the ability to register an account and log in using LinkedIn authentication. No password is needed so this is generally a more secure method of logging in.

LinkedIn authentication works by connecting your LinkedIn account with mailfloss.

If you already have an account registered with the same email address, the first time you try to log in using this method will link this authentication method with the account. And subsequent login attempts will succeed.

Give it a try and let us know what you think.

We’ve added the ability to register an account and log in using Google authentication. No password is needed so this is generally a more secure method of logging in.

Google Authentication works for personal Gmail addresses as well as Google Workspace business accounts.

If you already have an account registered with the same email address, the first time you try to log in using this method will link this authentication method with the account. And subsequent login attempts will succeed.

Give it a try and let us know what you think.

Many of you file uploaders often requested to keep the original data in the uploaded file and to append the mailfloss results to it. Well I’m happy to report that this is finally a reality for uploaded CSV files.

The generated appended file does take much longer to generate compared to just our report, but the option is there for those who want it.

You can initiate the process by visiting the Dashboard, clicking the “Export Emails” button and turning on the “Append results” option for the desired floss session.

Please note that this only works with CSV files and not Excel files.

We’ve added a category to detect if an email address failed Microsoft Exchange testing.

This category is extremely useful if you have many accept all domains in your email lists, as Microsoft Exchange is by far the largest email provider for businesses. With this new category, if the domain is using Microsoft Exchange there’s a good chance we can tell the difference between a real accept all address and a fake one.

This test is run by default through file upload and copy & paste. For our supported integrations, you can turn it on by setting your Aggressiveness Options to custom and selecting “failed exchange emails”, it is also included in the Aggressive setting.

One of our most requested options has finally arrived - custom decay protection schedules. Prior to this release, our decay protection would run once a month. Now, monthly is the default option, and in addition you can change the schedule to run weekly, twice a month, once every 2 months, 3 months, and 6 months. The schedule is also available on individual lists for some of our integrations.

To get started, go to the integration you wish to run a custom decay protection schedule on. Ensure Decay Protection is turned on, and then click the three vertical dots to set the desired schedule.

MailerLite has two versions, the classic version and the new. mailfloss now supports both. When you connect a new MailerLite account to mailfloss, the only difference now is an extra checkbox to indicate if the account is using MailerLite Classic or not.

We’ve updated our Klaviyo integration to use the new API endpoints, as the older API endpoints we were using are set to retire in 2024.

The migration is live and all Klaviyo accounts are now using these new endpoints. Please reach out if you have any questions or concerns regarding the migration.

Our Infusionsoft integration now supports custom fields updates. Previously, we relied on the tagging functionality, but we are migrating to custom fields as they are more appropriate for our purposes.

Custom field updating is available for use immediately on all Infusionsoft accounts subscribed to the Pro plan, as well as as an add-on to the Business and Lite plans.

Current customers using the tagging option are unaffected by this update, and are welcome to switch to custom fields updates instead.

We’ve added the ability to cancel floss sessions by API via the batch-verify cancel endpoint.

Please note that canceled floss sessions do not reimburse credits that have been used up during the floss session prior to canceling.

Refer to the developer documentation on how to use this endpoint.

We’re excited to announce the first version of our javascript widget.

Use this widget to embed on your forms, opt-ins, call-to-actions, popups, and so on.

The widget is especially useful if you don’t use a supported email service provider integration, as it allows for real-time verification at the point of entry.

Setup requires some technical knowledge and the ability to modify the HTML the widget will reside on.

Check out the developer documentation here.