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Cookie warm-up
Warm up the browser.
Opens a set of sites in the background, accepts their cookie banners, and closes them — so the profile looks lived-in before any signup.
Keep every inbox alive
An inbox that stays warm — never forgotten.
Mail Warmer auto-subscribes your email addresses to curated newsletters, so fresh inboxes keep receiving real mail and read as active, trusted accounts — ready to sign up for social, affiliate, and new services without getting flagged or blocked.
Free · no account · no inbox access · open source
- Day 0
You spin up a fresh inbox for a new project.
- Day 9
It sits empty. No mail in, no mail out.
- Day 21
Providers start flagging it as dormant.
- Day 34
You sign up somewhere with it — and get blocked.
- Day 48
The account gets limited, then quietly suspended.
- Tomorrow
It could just stay active on its own.
Why inboxes go cold
A quiet inbox is a dying inbox.
Providers trust accounts that look used. A silent inbox gets flagged as dormant and risks being limited or locked — right when you need it to sign up for social, affiliate, or a new account.
How it works
Watch the confirmations land.
Pick your emails and newsletters, hit Run, and each subscription drops a real confirmation into the inbox — live, one at a time, just like a person signing up by hand.
Live demo · looping
Inbox
Search mail
- Tech in Five nowConfirm your subscriptionOne tap to start getting Tech in Five each week.
- Morning Roast nowConfirm your subscriptionPlease confirm your email to get the daily Roast.
- The Daily Brief nowConfirm your subscriptionTap to confirm and get the brief every morning.
- Gmail Team 9:01Welcome to your new inboxTips for getting the most out of Gmail.
Three things it does
Quiet work that keeps inboxes alive.
Each demo below loops live — nothing is a video. They're the real states the extension moves through, staged on a mock.
Inbox cold warm
no new mail
Staying active
Inboxes stay warm.
Real newsletters arrive on their own schedule, so a fresh address reads as a living, trusted account — and stays usable for every signup you throw at it.
Brief
Roast
Tech5
Weekly
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b@…
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Status tracking
See every result.
Every email × newsletter is recorded — pending, running, done, or failed — so you always know exactly what landed and what to retry.
Ready when you are
Keep them
warm.
Keep them
warm.
Set it once, walk away.
Install Mail Warmer, add your emails, pick your newsletters — and your inboxes keep themselves active. No account, no setup. That's the whole deal.
Free · no account · no inbox access · open source
Small questions
The things people usually ask.
Does Mail Warmer read my email?
No. It never opens, reads, or sends from your inbox. It only fills out public newsletter signup forms with the addresses you give it. Everything runs locally in your browser; results live in chrome.storage.local. Every line is on GitHub.
Why does keeping an inbox warm matter?
A brand-new inbox that never receives anything looks dormant to email providers. Dormant accounts get flagged, rate-limited, or quietly suspended — and they're far more likely to be blocked when you use them to sign up for social media, affiliate networks, or new services. Steady incoming mail makes the account read as real and used, so it stays valid and ready when you need it.
Do I need to set anything up?
No. Install it, add your emails, and run. The curated newsletter list ships inside the extension and refreshes automatically in the background — there's no account to create and no server for you to host. If it ever can't reach the update server, it just keeps using the list it already has.
How does it actually keep an inbox warm?
It opens each newsletter's signup page in a background tab, detects the form, fills in your email (plus optional profile fields), and submits. Those newsletters then send mail regularly — so the inbox keeps receiving real messages and reads as an active, trusted account that providers are far less likely to flag, limit, or lock.
Is it going to cost money?
It's free and open source — no paywalls, no pro tier, nothing to host.
Which sites does it support?
Substack newsletters and generic HTML signup forms out of the box, via per-source adapters. The curated list ships with the extension, and we keep it updated for you.
Won't the signups look like spam?
It subscribes at a human pace, one newsletter at a time, and records the result per email × newsletter so you can see exactly what happened. It's opt-in subscribing to legitimate lists — not bulk or deceptive sending.