DFY GTM Systems

Cold Email Infrastructure Guide

By Abdul Sami, GTM Engineer · 8 min read · Last updated

Cold email infrastructure = separate sending domains + full authentication (SPF, DKIM, DMARC) + 2–3 mailboxes per domain + 2–4 weeks of warm-up + ongoing monitoring. Build it to be expendable: any single domain can burn without touching your primary domain or the rest of the fleet.

Sending domains

  • Buy lookalike domains: get-brand.com, brandhq.com, trybrand.io.
  • Never send cold from your primary domain.
  • Redirect each sending domain to your main site.
  • Enable auto-renew expired sending domains kill live campaigns.

Authentication stack

Each sending domain needs SPF (one record, -all), DKIM (2048-bit, enabled in the sending platform), and DMARC (start p=none with rua reporting, enforce to quarantine then reject). Check all three with the Domain Health Checker.

Mailboxes and providers

2–3 mailboxes per domain. Mix providers (Google Workspace + Microsoft 365) so a provider-level issue doesn't idle the fleet. Real names, real photos, complete signatures filters and humans both check.

Warm-up

New mailboxes ramp for 2–4 weeks: start at 5–10 emails/day with engagement (warm-up pools or manual), increasing gradually to the 25–30/day ceiling. Skipping warm-up is the most common way domains burn in week one.

Monitoring

  • Weekly: bounce rate, reply rate, spam placement tests.
  • Monthly: domain health check on every sending domain.
  • Instantly: pause any mailbox whose bounce rate exceeds 3%.

FAQ

How many sending domains do I need?
One domain (2–3 mailboxes) covers ~1,500 sends/month. Divide your volume target by that to size the fleet the Outbound Volume Calculator does the math.
Google Workspace or Microsoft 365 for cold email?
Both work; a mix is safest. Microsoft mailboxes are slightly cheaper, Google slightly better deliverability reputation run both and compare in your own data.
When is a domain burned?
When placement tests show consistent spam-foldering across providers despite clean content and low complaints. Retire it, fix the cause, and rotate in a rested domain.
AS

Abdul Sami

GTM Engineer, DFY GTM Systems

7+ years building outbound systems for B2B companies across the US, UK, Australia, and DACH. Specializes in Clay workflows, cold email infrastructure, intent-based lead sourcing, and deliverability.

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