KeepKnown | The Allow-List Email Filter for Gmail & Outlook

Popular inbox workflows

Start with the exact filter or search problem you have.

These guides cover the Gmail, Google Workspace, Outlook, and Microsoft 365 tasks people use before turning on strict contact-based screening.

Gmail filtering

Gmail Filter Sender Not in Contacts Gmail has no sender not in contacts filter. KeepKnown checks Google Contacts, moves unknown senders to KK:OUTSIDERS, and deletes nothing.
Gmail Filters Use Gmail filters to label, archive, categorize, forward, and mark email, then learn where Gmail filters stop and when contact-based screening is needed.
Gmail Only Allow Emails From Contacts Gmail cannot natively allow only emails from contacts. Use KeepKnown to screen non-contact senders into KK:OUTSIDERS while keeping every email recoverable.
How to Create Email Filters in Gmail Learn how to create email filters in Gmail, choose actions like labels and archive, apply filters to existing emails, and handle senders Gmail rules cannot express.
Gmail Filter Actions: Categorize As and Mark Important Use Gmail filter actions like Categorize as, Mark as important, Apply label, Skip Inbox, and apply filters to existing emails.
Gmail Filter Action Categorize As Use Gmail filter action Categorize as to route messages to Primary, Social, Promotions, Updates, or Forums, and know when category filters stop helping.
Apply Gmail Filters to Existing Emails Apply Gmail filters to existing emails with matching conversations, learn which actions affect old mail, and use KeepKnown for future unknown-sender screening.
Gmail Filter Multiple Keywords Create Gmail filters with multiple keywords using OR, quoted exact phrases, braces, sender groups, and subject terms, then know when keyword filters are not enough.
Gmail Filter Mark as Important Use a Gmail filter to mark matching mail as important, search is:important is:unread, and know why important markers do not stop unknown senders.
Gmail Auto Label Emails With Contacts Auto label Gmail email from unknown senders by comparing senders with Google Contacts and moving outsiders to a recoverable label.

Gmail search cleanup

Google, Outlook, and teams

Everything you need.

Nothing you don't.

You wouldn't leave your office door wide open for strangers to walk in and demand your attention. Why do it with your Inbox? KeepKnown is the Executive Assistant that screens every visitor at the door.

24/7 Vigilance

Real-time monitoring keeps your inbox clean round-the-clock. Every email is instantly checked against your contacts.

Auto Sync

Never miss newly added contacts. Everything syncs automatically from your email provider.

Custom Filters

Manage VIP access lists and domain filtering for complete inbox control.

Privacy First

Contacts are hashed for matching and encrypted for debugging. Never stored as plaintext. We never sell or share your data.

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Join thousands simplifying their inbox.

emails filtered and counting

Loved by professionals

See how KeepKnown helps people reclaim their inbox.

"KeepKnown has completely changed how we manage our inbox. We used to waste so much time sorting through junk mail — now it's clean, efficient, and stress-free. The spam control is spot-on, and we finally feel in control of our email again."

Taylor W.

Founder, NAPCO Pump Company

"I love KeepKnown, working quietly and diligently in the background, saving me hours of distraction. I don't know how anyone else manages their Inbox without it, or how this is not how everyone would want email to work. Bravo."

Paul N.

CEO, Intuitive

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Frequently Asked Questions

Everything you need to know about privacy, security, and how KeepKnown works.

No, we never read your emails. KeepKnown only checks the sender's email address against your contacts list. We don't access, store, or analyze the content of your emails. Your email content remains completely private.

No, your contacts are never stored as plaintext. We store a per-user one-way lookup token (HMAC-SHA256) for matching. For the debugger, we may also store an encrypted copy so you can view the actual address.

Absolutely not. Your information is never shared with, sold to, or used by any third party. Our business model is simple: you pay for the service, and that's it. We don't monetize your data.

Yes. KeepKnown has passed Google's security assessment (CASA Tier 2) and OAuth verification. Google has reviewed our app, verified our identity, and confirmed we handle your data securely.

Yes, always. We never delete emails - they're simply labeled and archived. Click the "KK:OUTSIDERS" label in your email client to see all filtered emails and move any back to your inbox with one click.

Still have questions? Contact our support team

Simple, transparent pricing

Choose the plan that fits your workflow. Connect your inbox first, then activate a 7-day trial with no charge today.

14 paying founders 959,762 outsider emails filtered Google verified

Starter

One public inbox protected by default

$ 29 23 / month

Less than the cost of 10 minutes of your time.

Billed annually ($276/year, save $72)

Or save $72/year with yearly billing

1 email account connected
Gmail, Outlook & Microsoft 365
Unlimited email filtering
Real-time contact sync
VIP access lists

Secure My Inbox

Create your account first. Add a card after inbox connection; no charge today.

Pro

Three inboxes for founders and small teams

Chosen by 13 paying founders

$ 60 48 / month

Less than the cost of 10 minutes of your time.

Billed annually ($576/year, save $144)

Or save $144/year with yearly billing

3 email accounts connected
Gmail, Outlook & Microsoft 365
Unlimited email filtering
Real-time contact sync
Priority support
Advanced analytics