4 free tools
Free cold email tools
Four tools we use when we set up cold email for customers. They run in your browser, need no sign-up and store nothing.
Tools
Pick a tool
- Cold email capacity calculatorDivide your monthly volume by 550: that is how many cold emails one mailbox sends in a month at 25 a working day. Add about 20% spare mailboxes, and put up to 5 mailboxes on each domain. 50,000 emails a month needs 91 sending mailboxes, 19 spares and 22 domains.Open the calculator
- SPF, DKIM and DMARC checkerEnter a domain to check its SPF record (one record, at most 10 DNS lookups, ending in ~all or -all), its DMARC policy, its DKIM keys and its MX records. Each finding says what breaks and how to fix it.Open the checker
- Spintax validatorPaste a subject line or an email with spintax. The validator reports unbalanced braces, empty options, spaces at option edges that get trimmed at send time, nested spintax, fallbacks inside spintax and nested fallbacks, then renders samples with filled and with empty merge fields.Open the validator
- Cold email copy checkerPaste the subject and body of a cold email. The checker flags links and bare domains (mail clients turn example.com into a link), images, spam-trigger phrases, fake Re: or Fwd: subjects, long emails, long sentences and missing questions, and says why each one matters.Open the checker
In your AI assistant
The same checks as agent skills
Download a SKILL.md and Claude, ChatGPT, Gemini, Grok or Cursor runs these checks on what you paste.
- Cold email copy reviewerCopy
- Cold email link checkerCopy
- Merge variable render checkCopy
- Cold email opener writerCopy
- Cold email spintax linterCopy
- Cold email subject line spintax generatorCopy
- Email blacklist check for IPs and domainsDeliverability
- SPF, DKIM and DMARC audit for sending domainsDeliverability
- Warm-up metrics readerDeliverability
- Cold email capacity plannerInfrastructure
- Cold email sending domain plannerInfrastructure
- All cold email skills21 skills
Mailboxes, warm-up and sending in one place
$2.50 a mailbox a month. DNS records are set for you, and every mailbox shows its warm-up numbers from day one.