A cold email sending domain is a separate domain you buy only to send outreach, such as getyouragency.com, so your main domain never carries the risk. Most agencies need one sending domain for every 300 or so businesses they contact each month, and each one costs about $11 in its first year.
This page covers the domain layer in detail: how many to buy, what to call them, where to buy them, how to set them up, and when to retire one. For how domains fit with mailboxes, warm-up, lists and copy, start with our guide to cold email for agencies.
What is a cold email sending domain?
A sending domain is a domain that exists only to send cold email and points visitors to your real website. It carries your brand name, it has its own mailboxes and its own DNS records, and it never sends your client email, invoices or password resets. Our guide to what a sending domain is explains how it protects your main domain.
People also call them secondary domains, outreach domains or domain variations. They all mean the same thing: a domain whose reputation you can afford to lose.
Why not send cold email from a subdomain or your main domain?
Use neither, because both put your main domain's reputation at risk. Inbox providers score every domain that sends to them, and a bad score on your main domain sends your everyday business email to spam as well.
A subdomain such as outreach.youragency.com looks like a safe middle ground, but it is not fully separate. Inbox providers weigh a subdomain's reputation against its parent domain, and a subdomain without its own DMARC record takes the parent's policy by default. Problems on the subdomain can still affect how providers see your main domain.
| Option | Risk to your main domain | Cost | Verdict |
|---|---|---|---|
| Your main domain | Direct: every complaint lands on it | $0 | Never for cold email |
| A subdomain (outreach.youragency.com) | Shared: it inherits and passes on reputation | $0 | Avoid |
| A separate sending domain (getyouragency.com) | None: it has its own reputation | About $11 a year | Use this |
How many sending domains do you need for cold email?
You need one sending domain for every 60 cold emails you want to send per weekday. That number comes from two safe limits: 2 mailboxes per domain, and 30 cold emails per mailbox per day. Our cold email mailboxes guide explains where those limits come from, and our guide to Google Workspace for cold email covers the most common mailbox provider.
To work it out, start from how many businesses you want to contact each month:
- Multiply businesses by emails per business. A 4-email sequence to 1,500 businesses is 6,000 emails.
- Divide by the sending weekdays in a month. 6,000 across 21 weekdays is 286 emails a day.
- Divide by 60 per domain and round up. 286 a day needs 5 domains and 10 mailboxes.
| Businesses contacted per month | Cold emails per month (4 each) | Emails per weekday | Domains needed | Mailboxes needed |
|---|---|---|---|---|
| 300 | 1,200 | 57 | 1 | 2 |
| 750 | 3,000 | 143 | 3 | 6 |
| 1,500 | 6,000 | 286 | 5 | 10 |
| 3,000 | 12,000 | 571 | 10 | 20 |
Buy one or two spare domains on top of the table. A spare that is already warm lets you swap out a tired domain without stopping your campaign for four weeks.
Other platforms publish looser limits. Smartlead's help center suggests 2 to 3 addresses per domain at up to 50 emails each, and Instantly's guide works from 3 accounts per domain at 40 a day. Those numbers can work, but they put more volume on each domain. We use the lower limits because a domain that sends less has less to lose.
How should you name cold email domains?
Name each sending domain as your full brand name plus one short, ordinary word. The prospect should recognize the business at a glance and never wonder whether the email is a scam.
Two patterns cover almost every case:
- A prefix before the brand: getacmedigital.com, tryacmedigital.com, joinacmedigital.com, theacmedigital.com.
- A suffix after the brand: acmedigitalhq.com, acmedigitalteam.com, acmedigitalgroup.com, acmedigitalstudio.com.
Avoid these, because each one makes a domain look throwaway to a reader or a filter:
- Shortened brands. "acmdgtl.com" saves letters and loses trust.
- Hyphens and numbers. "acme-digital-1.com" reads as a bulk sending domain.
- Spammy words. Free, deal, cheap, offer, fast and similar words belong nowhere in a domain.
- Lookalikes of other companies. A domain close to someone else's brand invites complaints and legal trouble.
Keep every sending domain in one family close to your real brand. Pipefire generates names this way: the full brand name, a short word such as "get", "hq" or "team", lowercase letters only, and .com first.
Which domain extension should you use for cold email?
Use .com wherever the name is available. It is the extension prospects trust most, and it carries no reputation baggage with spam filters.
When the .com is taken, .co, .net and .io are acceptable second choices. Avoid cheap extensions that spammers favor, such as .xyz, .top, .online, .biz and .info. A $2 domain on one of those can cost far more in lost replies than it saves.
Where should you buy cold email domains, and what do they cost?
Buy sending domains from a mainstream registrar that offers clean DNS management and fair renewal prices. A .com costs about $10 to $11 a year at cost-price registrars such as Cloudflare, and about $11 in the first year at Namecheap, rising to about $18 at renewal.
Always check the renewal price, not just the first-year price. Sending domains are meant to last more than a year, and a cheap first year with an expensive renewal costs more over the life of the domain.
The domain is the cheap part. The mailboxes on it cost more every month:
| Setup | Domains, first year | Domains, renewal year (Namecheap) | Mailboxes per month (Google Workspace at $7) |
|---|---|---|---|
| 3 domains, 6 mailboxes | about $33 | about $54 | $42 |
| 5 domains, 10 mailboxes | about $55 | about $90 | $70 |
| 10 domains, 20 mailboxes | about $110 | about $180 | $140 |
Prices are October 2026 list prices, with Google Workspace on an annual plan. Month to month it is $8.40 a user. Registrars run promotions, so the first-year figure is often lower.
Pipefire's Standard plan includes 10 sending domains and 20 mailboxes in the $497 monthly price, so there is nothing to buy or renew separately.
How do you set up a cold email sending domain?
A sending domain needs six things in place before it sends a single email: mailboxes, an MX record, SPF, DKIM, DMARC and a redirect to your website. Set them up in this order, because each step depends on the one before it.
- Add the domain to your mail provider and create the mailboxes. Two mailboxes per domain, with real first names, such as sarah@ and james@.
- Point the MX record at your mail provider. This tells the world where replies to the domain should be delivered.
- Add an SPF record. A TXT record that lists the servers allowed to send for the domain, such as Google's.
- Turn on DKIM. Your mail provider generates a key, you publish it as a TXT record, and every email you send is signed with it.
- Add a DMARC record. A TXT record at _dmarc that tells providers what to do when a message fails SPF or DKIM. Start with "p=none" and a reporting address, and tighten the policy once the domain has a clean sending history.
- Redirect the domain to your real website. A prospect who types the domain into a browser should land on your site, not a parking page.
Then check it. A free DNS lookup tool should show all four records, and a test email to a Gmail address should show SPF, DKIM and DMARC as "pass" in the message headers. Since February 2024, Google and Yahoo reject or junk bulk mail that fails these checks, according to Google's sender guidelines.
Pipefire does every step for you. Setup buys the domains, creates the mailboxes, publishes the records and checks they resolve before warm-up begins.
How long before a new domain can send cold email?
A new sending domain needs about 4 weeks before it sends at full volume. That is 14 days of warm-up, then 14 days of cold sending that rises from 5 to 30 emails a day per mailbox.
Warm-up builds a sending history, and our email warm-up guide covers the full schedule. Each mailbox exchanges a small number of normal emails that get opened and replied to, so inbox providers see a real person, not a new account blasting strangers.
A brand-new domain that skips this and sends 100 cold emails on day one is likely to land in spam within days. Buying domains early is the cheapest way to save time, because the 4-week clock starts the day the domain and mailboxes go live.
What happens when a cold email domain gets burned?
A burned domain is one whose reputation has dropped far enough that its mail lands in spam. The usual causes are too much volume too soon, a list with too many bad addresses, or too many people marking the emails as spam.
Watch for these signs:
- Warm-up mail starts landing in spam. The earliest and clearest warning.
- Bounces climb above 3%. A sign the list is bad, and a cause of further damage.
- Spam complaints pass 0.1%. Google asks senders to stay below 0.3%; act well before that.
- Replies stop while sends continue. Often the mail is quietly going to spam.
When you see them, stop cold sending from that domain at once, and keep the other domains running. A domain can sometimes recover with weeks of rest and warm-up only, but there is no guaranteed timeline. Because a replacement costs about $11, retiring a badly burned domain and swapping in a warm spare is usually the faster fix. Our burned cold email domain recovery guide covers how to confirm the damage and when recovery is worth it.
This is why separate domains matter. One burned domain out of ten is a small, cheap problem. A burned main domain is a business problem. Pipefire automatically pauses a campaign that crosses the bounce or complaint line; our deliverability page explains the thresholds.
Cold email domain FAQ
How many cold emails can one domain send per day?
Send no more than about 60 cold emails per domain per weekday: 2 mailboxes at 30 each. Some platforms allow more per domain, but lower volume per domain keeps each one safer.
Can I use the same cold email domains for several clients?
No. Give every client their own sending domains with their own brand name. Shared domains mix reputations, so one client's bad list can send another client's emails to spam.
Should a cold email domain have a website?
It should redirect to your real website. A visitor who types the domain should reach your business, which reassures both the prospect and the filters.
Do I need a separate Google Workspace account for each cold email domain?
No. One Google Workspace account can hold several domains, each with its own mailboxes. Each mailbox is still billed per user.
How long does a cold email domain last?
A well-run sending domain can be used for many months, and there is no fixed expiry. Retire it when its warm-up results, bounces or complaints show it has been damaged, not on a calendar date.
Is a brand-new domain bad for cold email?
New domains start with no reputation, which is why warm-up comes first. Some people prefer domains a few weeks old before sending; buying early and warming for 14 days covers that.