Your cold emails are going to spam. I know it because almost everyone who comes to us has the same problem. They wrote decent copy, built a solid list, but their infrastructure is garbage. So their emails never reach anyone.
Infrastructure is not the sexy part of cold email. Nobody wants to talk about DNS records and inbox warmup. But here is the truth: you can have the best email copy in the world and it will not matter if your sending setup is broken.
This is the guide I wish existed when I started. Everything you need to set up cold email infrastructure that actually lands in the primary inbox. Related: Cold Email Deliverability.
The Cold Email Infrastructure Stack
Your infrastructure has four layers. Mess up any one of them and your entire system fails. Related: B2B Cold Email Best Practices.
| Layer | What It Is | Why It Matters |
|---|---|---|
| 1. Domains | Separate domains for outbound | Protects your main domain reputation |
| 2. DNS Records | SPF, DKIM, DMARC | Proves you are a legitimate sender |
| 3. Email Accounts | Google Workspace or Outlook | Where emails actually send from |
| 4. Warmup + Rotation | Gradual volume increase + inbox cycling | Builds sender reputation |
Step 1: Domain Setup
Never send cold emails from your main domain. Ever. If your primary domain gets flagged, your entire company email goes down. Client communication, invoices, proposals, everything. Do not risk it. Related: Cold Email Compliance.
How Many Domains?
The formula is simple: one domain for every 50-100 cold emails per day. Each domain gets 2-3 email accounts. Each account sends 30-50 emails per day max.
| Daily Volume Goal | Domains Needed | Inboxes Needed |
|---|---|---|
| 100 emails/day | 2-3 | 4-6 |
| 300 emails/day | 5-6 | 10-15 |
| 500 emails/day | 8-10 | 20-25 |
| 1,000 emails/day | 15-20 | 40-50 |
Choosing Domain Names
Your secondary domains should look related to your main brand. If your main domain is acme.com, good options include:
- getacme.com
- acmehq.com
- tryacme.com
- acme.co
- meetacme.com
Avoid random domains that look nothing like your brand. "xj72sales.com" screams spam. Keep them professional and brandable.
Pro tip: Buy domains that are at least a few months old if you can. New domains have zero reputation and take longer to warm up. Check auction sites for aged domains in the $15-30 range. It saves you a week of warmup time.
Where to Buy Domains
- Namecheap: Best prices, easy DNS management
- GoDaddy: More expensive but works fine
- Google Domains (Squarespace): Simple if using Google Workspace
- Cloudflare: At-cost pricing, great DNS management
Step 2: DNS Configuration
DNS records tell email servers that you are a legitimate sender. Without them, your emails go straight to spam. No exceptions.
SPF (Sender Policy Framework)
SPF tells receiving email servers which IP addresses are allowed to send email from your domain. Without it, anyone could pretend to send from your domain.
Your SPF record looks something like this:
v=spf1 include:_spf.google.com ~all
If using Microsoft 365: v=spf1 include:spf.protection.outlook.com ~all
DKIM (DomainKeys Identified Mail)
DKIM adds a digital signature to every email you send. The receiving server verifies this signature to confirm the email was not tampered with in transit. Google Workspace and Microsoft 365 both generate DKIM records automatically. You just need to add the TXT record to your DNS.
DMARC (Domain-based Message Authentication)
DMARC tells email servers what to do when an email fails SPF or DKIM checks. Start with a monitoring policy:
v=DMARC1; p=none; rua=mailto:[email protected]
After a few weeks of monitoring, upgrade to quarantine or reject.
Check your records: After setup, use MXToolbox or mail-tester.com to verify everything is configured correctly. A single typo in a DNS record can tank your deliverability. Check it before you send a single email.
Step 3: Email Account Setup
Google Workspace vs Microsoft 365
| Factor | Google Workspace | Microsoft 365 |
|---|---|---|
| Price per inbox | $6/month | $6/month |
| Gmail deliverability | Better | Good |
| Outlook deliverability | Good | Better |
| Setup difficulty | Easy | Easy |
| Tool compatibility | Excellent | Excellent |
Best approach: use both. Put half your domains on Google Workspace and half on Microsoft 365. This diversifies your sending infrastructure and covers both major email ecosystems.
Creating Email Accounts
Use real-looking email addresses. First name, first name + last initial, or first.last format. These look like normal business emails:
Avoid: sales@, info@, outreach@, or anything that screams "this is a marketing email."
Step 4: Domain and Inbox Warmup
This is where most people screw up. They buy domains, set up DNS, and immediately start blasting cold emails. Their deliverability tanks within days.
New domains and inboxes have zero reputation. Email providers do not trust them. You need to build that trust gradually.
Warmup Process
| Week | Emails Per Inbox Per Day | What You Are Doing |
|---|---|---|
| Week 1 | 5-10 | Warmup tool conversations only |
| Week 2 | 15-25 | Warmup tool + a few manual cold emails |
| Week 3 | 25-40 | Ramping up cold email volume |
| Week 4+ | 30-50 | Full sending volume, warmup continues in background |
Warmup Tools
These tools send and receive emails between your inboxes and a network of other inboxes. They open them, reply, mark as "not spam," and move to primary. This trains email providers that your inbox is legitimate.
- Instantly: Built-in warmup with their sending platform. Most popular option.
- Smartlead: Unlimited warmup included with sending.
- Warmbox: Standalone warmup tool. Good if you use a different sending platform.
- Mailreach: Focus on warmup quality over volume.
Critical rule: Never stop warmup. Even after your inbox is fully warmed, keep the warmup tool running at a low level (5-10 interactions per day). This maintains your sender reputation over time. The moment you stop, reputation starts to decay.
Step 5: Inbox Rotation
Inbox rotation distributes your cold email sends across multiple inboxes automatically. Instead of one inbox sending 200 emails, 5 inboxes each send 40. This keeps each individual inbox below the radar and protects sender reputation.
How Rotation Works
- You create a campaign with your email sequence
- You assign multiple sending accounts to the campaign
- The tool automatically rotates which inbox sends each email
- Follow-ups stay on the same inbox for conversation continuity
Rotation Best Practices
- Never send more than 50 cold emails per inbox per day
- Space emails out with random delays (2-5 minutes between sends)
- Use different sending windows (not all emails at 9am)
- Monitor bounce rates per inbox. If one starts bouncing, pause it.
- Replace underperforming inboxes regularly (every 2-3 months)
The Complete Infrastructure Checklist
- Buy 3-5 secondary domains (brandable, similar to main domain)
- Set up Google Workspace or Microsoft 365 on each domain
- Create 2-3 email accounts per domain
- Configure SPF, DKIM, and DMARC for every domain
- Verify DNS records with MXToolbox
- Connect all inboxes to a warmup tool
- Run warmup for 2-3 weeks before sending cold emails
- Set up inbox rotation in your sending tool
- Start with 10-20 cold emails per inbox per day
- Gradually increase to 30-50 per inbox per day over 2 weeks
- Monitor deliverability weekly (open rates, bounce rates)
- Keep warmup running in perpetuity
Common Infrastructure Mistakes
- Sending from your main domain: One spam flag and your entire business email is compromised.
- Skipping warmup: Sending 100 emails from a brand new inbox gets you blacklisted immediately.
- Missing DNS records: Forgetting DMARC or having a broken SPF record tanks deliverability silently.
- Too much volume per inbox: Sending 100+ emails from a single inbox is a red flag for email providers.
- Not monitoring: Deliverability changes over time. Check your metrics weekly and rotate inboxes that underperform.
- Using cheap email providers: Free email accounts (Gmail, Outlook.com) are not designed for outbound. Use business accounts.
Monthly Infrastructure Cost
| Component | Cost | For 300 emails/day setup |
|---|---|---|
| Domains (5) | $10-15 each/year | ~$6/month |
| Google Workspace (15 inboxes) | $6/inbox/month | $90/month |
| Warmup tool | Included with sending tool | $0 extra |
| Sending tool (Instantly/Smartlead) | $30-97/month | $97/month |
| Total | ~$193/month |
Under $200 per month for infrastructure that lets you send 300 emails per day. That is 6,000+ cold emails per month. If those emails book even 10 meetings, the ROI is absurd.
Frequently Asked Questions
How many domains do I need for cold email?
Start with 3-5 domains for every 100 emails per day you want to send. Each domain should have 2-3 inboxes. So for 300 emails per day, you need about 5 domains with 15 total inboxes. Scale up as volume increases.
How long does domain warmup take?
Plan for 2-3 weeks minimum. Start by sending 5-10 emails per inbox per day and gradually increase by 5-10 per day. After 3 weeks, each inbox should handle 30-50 cold emails per day safely.
Should I use Google Workspace or Outlook for cold email?
Both work. Google Workspace has slightly better deliverability to Gmail inboxes. Outlook (Microsoft 365) has better deliverability to corporate Outlook inboxes. Ideally, use both to diversify your sending infrastructure.
What DNS records do I need for cold email?
You need three records: SPF (tells email servers which IPs can send from your domain), DKIM (digitally signs your emails to prove authenticity), and DMARC (tells servers what to do with emails that fail SPF or DKIM checks). All three are required for proper deliverability.
Want Us to Set Up Your Infrastructure?
ColdCraft handles the entire cold email infrastructure buildout. Domains, DNS, warmup, rotation, and ongoing monitoring. You focus on selling.
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