Warmerly is an email deliverability SaaS built by a developer who needed it himself. Mailbox warmup automation, deliverability monitoring, and sender reputation protection — for businesses that live and die by their inbox placement rate.
Most businesses do not think about email deliverability until their open rates crater, their replies stop coming, and their cold outreach pipeline dries up overnight. By then, Google and Microsoft have already quietly moved their sending domain to a reputation category that makes inbox placement nearly impossible.
The filters that decide where your email lands — Gmail's neural classifier, Microsoft SmartScreen, Yahoo's reputation engine — operate continuously and silently. They score every signal: whether recipients reply, whether mail gets moved out of spam, whether the domain has a clean authentication chain, whether sending volume matches the historical pattern. Get a single signal wrong at the wrong moment and you are in Promotions. Get several wrong and you are in spam. Stay there long enough and your domain is burned.
The tragedy is that this is almost entirely preventable. Proper warmup, consistent authentication monitoring, and reputation-aware sending volume are enough to keep almost any honest sending domain out of trouble. But almost nobody does it systematically, because until recently the tooling was either prohibitively expensive or embarrassingly crude.
Most businesses discover deliverability problems too late
A domain that has spent weeks in spam is far harder to recover than one that never got there. Prevention costs pennies; recovery costs campaigns.
Volume ramps are not optional
New mailboxes and domains need a gradual, reputation-matched ramp. Sending 500 cold emails from a week-old mailbox is not aggressive — it is a fast track to a permanent spam folder.
Authentication is table stakes, not a bonus
SPF, DKIM, and DMARC misconfigurations are responsible for a significant portion of deliverability failures. They are also entirely avoidable.
Warmup tooling has been broken
Random single-line emails between bot accounts do not produce the signals Gmail and Outlook actually reward. Real contextual threads with real replies do.
Kristiyan Tsvetanov is a developer, product builder, and founder based in Birmingham, UK. He started writing code commercially in his teens and has since built multiple software products across web development, SaaS, AI content, EdTech, and now email deliverability.
His approach is consistently the same: identify a problem he is experiencing directly, build a focused tool to solve it, and release it as a product for others in the same situation. Warmerly is the clearest expression of that philosophy to date.
Kristiyan handles everything at Warmerly: architecture, product design, engineering, growth, and strategy. He believes software should work reliably, explain itself clearly, and stay out of the way of the person using it.
A Birmingham-based web design and development studio serving small and medium businesses across the UK. TsvWeb is where Kristiyan first encountered the cold email deliverability problem at scale.
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Running growth at TsvWeb meant running cold email outreach: prospecting, sequencing, follow-ups. It works — when it reaches the inbox. After a particularly damaging episode in which a domain he had carefully built for outreach landed in spam across the majority of recipients and took weeks to recover, Kristiyan started auditing every variable in the system.
He discovered that the existing warmup tools on the market were either too expensive for a small studio to justify, too shallow to produce the signals that actually matter to Gmail and Outlook, or both. The better-known names relied on patterns that had worked in 2019 but that modern filters had learned to discount or penalise.
He spent several months reverse-engineering what the filters actually reward — studying Google Postmaster Tools data, Microsoft SNDS signals, and academic research on email classification — and built a prototype that implemented those signals properly: contextual threads, spam recovery automation, reputation-matched peer selection, and per-provider routing logic.
The prototype worked. Domain health scores improved within two weeks. Inbox placement rates returned to above 90 percent. He packaged the prototype into a product, added a dashboard, and launched Warmerly.
"Every deliverability tool I tried either cost too much for what it did, or did the wrong things efficiently. I needed something that understood what Gmail actually scores, not what worked five years ago."
Cold email only works if it reaches the inbox — everything else is noise.
Domain reputation is an asset. It takes months to build and days to destroy.
Authentication errors are silent killers. You rarely know until your open rate collapses.
Volume ramps are not optional. Sending at scale from a fresh mailbox is how you get blacklisted.
No tool was fixing these problems properly. So he built one.
Warmerly is not a single-trick warmup tool. It is a deliverability platform built around the complete set of signals that modern email filters actually score.
Warmerly generates multi-turn threaded conversations — with proper subjects, quoted replies, and natural latency — between real OAuth-connected mailboxes. Not robotic pings. The signals Gmail and Microsoft reward.
Daily SPF, DKIM, DMARC, MX, and TLS checks across every connected mailbox. Authentication failures surface before they cost you a campaign, not after. Health scores updated after every warmup batch.
Seed recipients across Gmail, Outlook, Yahoo, and ProtonMail tell you exactly which folder your mail is hitting — Primary, Promotions, Updates, or Spam. Per-provider breakdown over 30 days.
Warmerly's peer network scans the spam folder every 10 minutes. When warmup mail is misclassified, it is automatically marked not-spam, starred, replied to, and moved back to the primary inbox — the single strongest positive signal the filters track.
Connect Google Workspace, Microsoft 365, and generic IMAP mailboxes side by side. Group by client or campaign. Set per-mailbox ramp curves, health score floors, and alert thresholds. Agency-grade without agency-grade pricing.
Warming a new mailbox against only other new mailboxes is a red flag. Warmerly pairs new accounts primarily with aged, trusted peers and gradually introduces newer correspondents as your reputation climbs.
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Warmerly is built and run by Kristiyan. He owns every layer: the product roadmap, the technical architecture, the go-to-market strategy, and the day-to-day business decisions. There is no committee, no quarterly planning cycle, and no layer of management between a customer's feedback and the person who can act on it.
This means Warmerly moves quickly and stays focused. Features that solve real deliverability problems get shipped. Features that exist only to look good on a comparison page do not. The roadmap is driven by the signal that matters most: what are paying customers actually asking for?
Kristiyan's background across TsvWeb, Vonlix, Scribtly, and The Revision Hub means he understands the operational context that Warmerly's customers live in: founder-led sales teams, lean marketing operations, and growth functions where every tool needs to earn its seat on the stack.
Product vision
Kristiyan defines what Warmerly is, what it is not, and what it will become. The core principle: solve the complete deliverability problem, not the easiest 20 percent of it.
Technical development
He architects and engineers the warmup engine, the monitoring pipeline, the health scoring system, the peer selection algorithm, and the dashboard. The entire stack is his.
Business direction
Pricing, positioning, partnerships, and growth channels are all run directly by Kristiyan. No agency, no growth consultant — just a founder who understands his market because he is in it.
Customer relationships
Support emails go to Kristiyan. Feature requests land on his desk. When something is broken, he is the one fixing it. Customers get direct access to the person who built the product.
Warmerly is one part of a broader portfolio of software products and services. If you are curious about the person behind the product, these links are where to start.
Connect your first mailbox in under 60 seconds. Warmup starts immediately and you will see your first health score within 24 hours.