ColdMail Filter: regex cold-email blocker

A self-hosted inbox filter for freelancers and small teams drowning in cold sales emails

Problem

A developer shared that he was flooded with cold sales emails daily and ended up writing a script that scans Gmail every ten minutes, blocking obvious pitches with a set of regexes and falling back to AI for the rest. Many people don't want to hand their inbox content to a third-party SaaS, but also can't build and maintain these rules themselves.

Solution

A self-hostable email filtering assistant: ships with a continuously updated library of cold-email regexes and phrasing patterns that users import into Gmail/Outlook rules with one click; calls the user's own LLM API key for borderline cases; and provides a dashboard to review blocked mail and tune rules, with all data staying in the user's own account.

Users

Freelancers, indie developers, small-team founders, recruiters and salespeople who receive large volumes of unsolicited pitches.

MVP

One-click Google Apps Script installer; built-in cold-email regex library with custom rules; optional bring-your-own OpenAI/Claude key for a second pass; weekly block-summary email; exportable whitelist for false positives.

Revenue

Free open-source core to build trust; paid tier for a hosted rule-update feed, a multi-mailbox dashboard and team-shared whitelists at $3-6/month.

Why now

AI has driven the cost of generating cold emails to near zero, so inbox pollution will only get worse; meanwhile personal LLM API keys are now ubiquitous, making local classification feasible for an indie developer without competing head-on with the big anti-spam players.