About
We're building cold email infrastructure that respects the inbox.
MailFlow started in 2025 after the founder spent six months trying — and failing — to keep cold outreach landing in the inbox using existing tools. Every shortcut these tools took (shared IPs, vendor APIs with restricted scopes, opaque "warmup as a service") made the deliverability problem worse for the customer. So we rebuilt the stack from the protocol up.
Our thesis
Cold outreach should travel through the protocols email was designed for: SMTP and IMAP. Restricted Google API scopes are a vendor lock-in tax that makes the product worse for everyone — slower onboarding, $500–2,500 per year in CASA fees, hard caps on how many users you can serve.
With App Passwords, all of that disappears. You connect any inbox in 60 seconds, the warmup engine speaks IMAP commands the way real humans do, and your sending reputation belongs to you — not to a third party.
By the numbers
- 4,200+
- Active workspaces
- 18M
- Sends per month
- 83%
- Avg inbox placement
- <60s
- Median reply latency
- 12+
- RBLs checked per scan
- $0
- CASA verification cost
What we believe
Inbox first
Every product decision is graded against one question: does this help our users land in the inbox?
Be the un-OAuth
Standard SMTP and IMAP have worked for 30 years. We refuse to lock our customers into vendor APIs.
Honest deliverability
No magic warmup. We tell you exactly which IMAP commands run and why.
Ship boring infra
Cron jobs, queues, retries with backoff. The unsexy stuff is what stops mail from getting lost.
Default to private
Encryption at rest, audit logs, redacted credential paths. Privacy is not a tier.
Respect the recipient
CAN-SPAM and GDPR compliance is enforced by the product, not the user.
Team
Previously built outreach infra at two SaaS companies. Tired of losing 70% of replies to spam.
Spent 6 years on email infrastructure at a deliverability ESP. Knows what makes Gmail say no.
Ex-growth at a Y Combinator B2B startup. Cares about every pixel of the campaign builder.
Built design systems at Linear-adjacent startups. Believes Cmd+K should work everywhere.
Hiring engineers, deliverability specialists and customer success. Say hi →