Cold email infrastructure, set up and warmed before it reaches you

The domains, mailboxes, DNS records and warm-up that cold email depends on, done before sale and sold by the domain. You bring the list, the copy and the sequencer.

zone: northfieldgrowth.comExample

Lookup: dig +short TXT google._domainkey.northfieldgrowth.com

"v=DKIM1; k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAvq3…"

DKIM

Signs every message, so a receiver can check it really came from the domain and was not altered.

Example zone. Pick a record to see its lookup and what it does.

What cold email infrastructure is

Cold email infrastructure is everything that has to exist between "we have a list and a message" and "the message arrives in an inbox". It is easy to underestimate because none of it is visible in a campaign report, yet every part of it can quietly decide whether your emails are read or filtered.

For most teams it comes down to six parts:

Part	What it is	Who handles it with InboxesNow
Sending domains	Domains used only for outreach, separate from your main company domain	Included with every purchase
Mailboxes	Real inboxes on a reputable email platform	Google Workspace, 3 per domain
Mail DNS	MX, SPF, DKIM and DMARC records	Published before sale
Tracking domain	A domain of your own for open and click tracking	A custom tracking domain for Instantly, on every domain
Warm-up	A gradual sending history before real campaigns	At least 21 days on every inbox before sale
Sequencer	The tool that sends your campaigns and follow-ups	Yours: Instantly, Smartlead, Lemlist or another

The rest of this page walks through each part, what goes wrong with it, and what is already done when you buy.

Sending domains

Outreach is usually sent from domains set aside for it rather than from your company's main domain. The reason is risk: if an outreach domain's reputation suffers, your main domain, and the everyday mail your team sends from it, is not affected. It also lets you spread volume across several domains instead of loading one.

Every InboxesNow domain is a sending domain of this kind. It is included in the price, and it comes with 3 inboxes already on it.

Mailboxes on Google Workspace

The mailboxes are real Google Workspace inboxes, the same Gmail that many businesses use for their own mail, each named for a person with a realistic US first and last name. That matters for two reasons: mailbox providers see mail coming from an established platform, and your recipients see a normal sender rather than an obviously generated address.

Mail DNS: MX, SPF, DKIM and DMARC

Four DNS records do most of the work of proving that mail from a domain is genuine:

MX routes mail for the domain to its Google Workspace inboxes, so replies arrive.
SPF lists the servers allowed to send for the domain.
DKIM signs every message, so a receiver can check it came from the domain and was not altered.
DMARC tells receivers what to do when SPF or DKIM fail, and where to send reports.

Getting these right by hand is fiddly: a second SPF record, a DKIM key that was never switched on, or a typo in DMARC can each undo the rest. On every InboxesNow domain all four are published before the domain goes on sale, so there is nothing to paste into a DNS panel. The example zone above shows the records and the lookups that check them, and the guide to SPF, DKIM and DMARC for cold email explains each one in plain words.

The daily placement test also records whether SPF, DKIM and DMARC passed on each day's test messages, so the inbox placement record doubles as a running check that authentication is still working.

A custom tracking domain

If you track opens or clicks, your sequencer rewrites links and adds a tracking pixel. By default those point at the sequencer's shared tracking domain, which many senders share. A custom tracking domain points them at a subdomain of your own sending domain instead. Every InboxesNow domain has a custom tracking domain for Instantly already set up as a CNAME record.

Warm-up, with a record to show for it

A new domain with new inboxes has no reputation, and sending campaigns from it straight away is the fastest way to land in spam. Every InboxesNow inbox is warmed for at least 21 days before it goes on sale, and every domain shows its warm-up record before you buy: days warmed, the daily warm-up chart, the 7-day warm-up inbox rate and a health score.

Sizing it: how many domains and inboxes

Capacity comes from the number of inboxes, not from pushing each one harder. By default each inbox sends up to 30 campaign emails a day alongside its warm-up, which is 90 a day per domain. For 900 emails a day you need 10 domains: 30 inboxes, $150 a month. The guide on how many inboxes and domains you need works through larger volumes and explains why to keep a little spare capacity.

Connecting your sequencer

The infrastructure is only useful once your sequencer can send through it. There are two ways to hand it over:

Instantly: connect your workspace with an API key, and each inbox moves in with one Google sign-in, verified on a live delivery board. See pre-warmed inboxes for Instantly.
Any other sequencer: release the domain, take each inbox's address and password (and a CSV), and connect them with Google sign-in in Smartlead, Lemlist or any tool that connects Google Workspace inboxes. Our warm-up stops at release. See pre-warmed inboxes for any sequencer.

What stays with you

Infrastructure gets your mail a fair hearing; it cannot make a poor campaign good. Three things stay in your hands:

Your list. Verify addresses before sending: bounces damage a sender's reputation quickly.
Your volume. Ramp up gradually and stay within sensible daily limits per inbox.
Your message. Write to a person, keep links and images light, and make it easy to say no.

Terms like sending domain, tracking domain and DMARC alignment are defined in the deliverability glossary. For what each domain costs, see pricing.