How to Set Up Cold Email Infrastructure from Scratch

Most cold email fails before a single message is written. The problem is not copy, targeting, or timing — it is infrastructure. Your emails never reach the inbox because the sending setup was rushed or misconfigured.

This guide covers the exact infrastructure setup we deploy for every GTMinds client before a single outbound email goes out. Follow this sequence and you will start with 60%+ open rates instead of fighting your way out of spam folders.

Step 1: Buy Secondary Domains

Never send cold email from your primary domain. If your company domain is acme.com, buy secondary domains for outbound:

• acme-team.com, getacme.com, tryacme.com, acmehq.com

• Buy 3–5 secondary domains per sending campaign

• Use different registrars (Namecheap, Cloudflare, Google Domains) to avoid pattern detection

Why multiple domains? If one domain gets flagged, your other campaigns keep running. It also lets you spread volume across domains — 30–50 emails per mailbox per day is the safe ceiling.

Step 2: Configure DNS Records

Every secondary domain needs three DNS records configured correctly. Miss any one and your deliverability suffers.

SPF (Sender Policy Framework)

SPF tells receiving servers which mail servers are authorized to send email from your domain. Add a TXT record:

• For Google Workspace: v=spf1 include:_spf.google.com ~all

• For Outlook/Microsoft 365: v=spf1 include:spf.protection.outlook.com ~all

DKIM (DomainKeys Identified Mail)

DKIM adds a cryptographic signature to your emails proving they come from your domain. Your email provider (Google Workspace or Microsoft 365) generates the DKIM key — you add it as a DNS TXT record. This is non-negotiable for deliverability.

DMARC (Domain-based Message Authentication)

DMARC ties SPF and DKIM together and tells receiving servers what to do with messages that fail authentication. Start with a monitoring policy:

v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com

After 2–4 weeks of monitoring, move to p=quarantine and eventually p=reject as you confirm everything is configured correctly.

Step 3: Create Mailboxes

Set up 2–3 mailboxes per secondary domain. Use real-sounding names:

• neeraj@acme-team.com, sarah@acme-team.com

• Avoid generic addresses like sales@, info@, or outreach@

• Each mailbox should have a profile photo, display name, and email signature

Google Workspace ($7/user/month) or Microsoft 365 ($6/user/month) are the standard choices. Some teams use Outlook for better deliverability to corporate recipients, but Google Workspace is more widely used and easier to manage at scale.

For bulk setup, services like InboxKit can provision and configure multiple mailboxes at once — useful when you need 20+ sending accounts.

Step 4: Warm Your Mailboxes

New mailboxes have no sending reputation. If you start blasting cold emails from day one, you will land in spam immediately. Warmup is mandatory.

How warmup works:

1. Connect your mailboxes to a warmup network (Instantly and Smartlead both have this built in)

2. The warmup system sends and receives emails between real mailboxes in the network

3. Replies are automatically generated to simulate real engagement

4. Emails that land in spam are automatically moved to inbox (training spam filters)

Warmup timeline:

• Week 1–2: Warmup only. No outbound. Start at 5 warmup emails/day, ramp to 30.

• Week 3: Begin sending 10–15 cold emails/day alongside warmup.

• Week 4+: Ramp to 30–50 cold emails/day per mailbox. Keep warmup running permanently.

Never turn off warmup. Even after your mailboxes are established, warmup maintains your sender reputation by keeping positive engagement signals flowing.

Step 5: Connect Your Sending Tool

We use Instantly for most client deployments. Smartlead is a strong alternative. Both handle the critical infrastructure pieces:

• Mailbox rotation — automatically rotates between your sending accounts so no single mailbox exceeds daily limits

• Built-in warmup — both platforms have warmup networks, eliminating the need for a separate warmup tool

• Reply detection — automatically pauses sequences when a prospect replies, preventing awkward double-sends

• Bounce handling — automatically removes bounced emails and flags problematic addresses

Connect all your mailboxes to the sending tool, assign them to a rotation pool, and configure sending windows (typically 8 AM–6 PM in your prospect's timezone, weekdays only).

Step 6: Monitor Deliverability

Setup is not a one-time event. You need ongoing monitoring:

• Track open rates per mailbox — if a mailbox drops below 40% opens, pause it and investigate

• Monitor bounce rates — keep bounces under 3%. Above that, your list quality is the problem

• Check spam placement weekly — tools like mail-tester.com or GlockApps show where your emails land

• Rotate flagged domains — if a domain's reputation drops, stop sending from it, keep warmup running for 2–4 weeks, then reintroduce slowly

The investment in infrastructure pays for itself immediately. Teams that skip this process waste months fighting deliverability issues. Teams that follow it start generating replies from week three.