Infrastructure Setup: DNS & Deliverability

An email that lands in spam did not exist — here is the unglamorous foundation that determines whether everything else works

Before you write a single email you need to solve deliverability. It does not matter how well the email is written if it never reaches the inbox.

This lesson is the foundation that everything else depends on.

The First Rule: Never Send From Your Main Domain

If your business email is alex@yourcompany.com do not send cold outreach from that address. Ever.

When you send hundreds of cold emails from your primary domain and some get marked as spam, which they will even from a great campaign, you risk damaging your main domain's reputation. That means your regular client emails, invoices, and proposals start landing in spam folders too. The cost is catastrophic.

Instead buy a sending domain: a variation of your main domain used exclusively for outbound.

Examples: if your main domain is voho.ai your sending domain options could be outreach.voho.ai, hello.voho.ai, or tryvoho.com. If your main domain is alexbuilds.com you could use hi.alexbuilds.com or team.alexbuilds.com.

Buy the sending domain from Namecheap or Cloudflare Registrar. Cost is roughly $10 to $12 per year.

DNS Records: SPF, DKIM, and DMARC

These three records tell receiving email servers that your emails are legitimate. Without them, major providers like Google and Yahoo reject your emails entirely in 2026. Not just filter. Reject.

SPF (Sender Policy Framework) tells email servers which servers are allowed to send on your behalf.

DKIM (DomainKeys Identified Mail) adds a cryptographic signature to every email you send proving it has not been tampered with.

DMARC tells servers what to do with emails that fail SPF or DKIM and sends you reports.

If you are using Instantly.ai which is the recommended tool, it generates the exact DNS records you need in its domain setup flow. Copy them into your domain registrar's DNS settings.

If you are connecting a Gmail address instead, use these records.

SPF record as a TXT record at @ or your sending domain:

• v=spf1 include:_spf.google.com ~all
• DKIM is generated in Google Workspace Admin under Apps then Gmail then Authenticate Email. Copy the TXT record it gives you.

DMARC record as a TXT record at _dmarc.yourdomain.com:

v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com; pct=100

DNS changes take 24 to 48 hours to propagate. Verify your setup at MXToolbox.com by entering your domain and running the SPF, DKIM, and DMARC checks. All three should show green.

Domain Warmup

A brand new domain has zero reputation. If you start sending 50 emails a day from it on day one it will be flagged as spam immediately.

Warmup is the process of gradually increasing your sending volume so email providers build a positive reputation for your domain.

The 4-week warmup protocol works as follows.

In Week 1 send 5 to 10 emails per day using the warmup tool only with no real outreach yet.

In Week 2 send 15 to 20 emails per day and you can start sending to 5 to 10 real prospects per day.

In Week 3 send 25 to 30 emails per day and gradually increase real outreach.

In Week 4 and beyond send 35 to 50 emails per day at full sending capacity.

Warmup tools that automate this process by having your new inbox send and reply to other inboxes in a network include Instantly.ai which has built-in warmup included in all plans and is the recommended option, Warmup Inbox which is a standalone warmup tool if you are not using Instantly, and Mailreach as an alternative option.

Leave warmup running in the background permanently even once you reach full capacity. It maintains your reputation over time.

Daily Sending Limits

The safe sustainable limit for cold emails in 2026 is 35 to 50 per day per inbox.

This is lower than many tools suggest and lower than what is technically possible. It is the right number because staying under it keeps your spam complaint rate below the 0.3% threshold that triggers Google's enforcement, it forces you to be selective about who you send to which improves quality, and it is sustainable so you will not burn through lists or domain reputation.

If you need to send more than 50 per day, create a second sending domain and inbox and not a second sending address on the same domain. Each inbox on its own warmed-up domain.

Testing Before You Send

Before your first real campaign send test emails and verify four things.

First confirm you land in the inbox and not spam by using Mail Tester at mail-tester.com. Aim for a score of 9 out of 10 or above.

Second confirm SPF, DKIM, and DMARC are all passing by checking MXToolbox.

Third confirm warmup has been running for 14 or more days by checking the Instantly dashboard.

Fourth confirm your sending limit is configured in your sending tool before launching.

Use this Claude prompt before every new campaign:

Review my sending setup for my outbound email campaign.

Sending domain: [DOMAIN]
Warmup started: [DATE]
SPF/DKIM/DMARC: [STATUS FROM MXTOOLBOX]
Daily limit set: [NUMBER]
First campaign planned: [DATE]

Tell me if anything needs to be fixed before I send.

Adding to EMAIL.md

## Sending Infrastructure
Sending domain: [YOUR SENDING DOMAIN]
Email address: [NAME]@[SENDING DOMAIN]
Warmup started: [DATE]

Warmup tool: Instantly.ai or Warmup Inbox

Daily limit: 40 emails per day

DNS verified: SPF confirmed, DKIM confirmed, DMARC confirmed

Last MXToolbox check: [DATE]

Your Action Right Now

Buy your sending domain. Set up the DNS records. Start the warmup. This takes 30 to 45 minutes today and 14 days to complete automatically in the background.

You can write your emails in the next lessons while the warmup runs. By the time you have finished the course the domain will be ready.