Separate Sending Domain: How to Choose and Set One Up
Cold email should not go out from your company's main domain. Here is why, how to choose a domain name, which steps to take and how many inboxes you need.
Why you need a separate sending domain
A separate sending domain protects your company's main domain. Cold email tends to draw more spam complaints and bounces than ordinary correspondence. If that hits the main domain, quotes, invoices and emails to existing customers risk ending up in the junk folder too. With a domain of its own, the damage stays where it started.
Imagine a salesperson sending a first wave from examplecompany.se. A few recipients mark the email as spam, a few addresses turn out to be dead, and after a couple of days emails from the finance department start landing in customers' spam folders. Nobody has made an obvious mistake. But sender reputation belongs to the domain, and that is the very domain all your regular email shares. Repairing a reputation takes time, and in the meantime you cannot tell which customer emails never arrived.
So the rule is simple: email where you don't know how the recipient will react is not sent from the same domain as email where the relationship already exists. That holds even if you send few emails and are careful. Caution reduces the risk but does not remove it. Small volumes and targeted emails keep the new domain healthier, but it is the separation that turns a mistake into a contained mistake.
How to choose a domain name
The name should be recognizable. A recipient who types the domain into a browser should understand who sent the email. A name that can't be linked to your company looks like exactly what many people think cold email is.
A few rules of thumb that work:
- Take the company name and add a word before or after it, for example getexamplecompany.se or examplecompany-team.se.
- Choose the country extension that matches your market. If you sell to Sweden, .se is the natural choice, and .com works as an alternative. Avoid unusual extensions that are rarely used in business.
- Avoid hyphens in the middle of the name, numbers and long constructions. They look suspicious and are hard to say aloud.
- Check that the domain has no history. A used domain can carry a bad reputation that you won't see until it is too late.
Have the web address of the new domain redirect to the company's real website. Anyone who clicks or looks up the domain then lands in the right place, and it shows that the sender is real.
Subdomain or a domain of its own?
Sometimes a subdomain is suggested, for example mail.examplecompany.se. It can be done, and it is better than sending from the main domain. But a subdomain is tied to the main domain, and receiving systems may let the reputations affect each other in both directions. A fully separate domain is cleaner.
Our recommendation: choose a domain of its own as soon as cold email is a recurring channel. A subdomain is enough as a first step if you only want to test on a small scale and don't want to buy anything new yet. In that case, expect to change your setup if volumes grow.
How to set up a separate sending domain, step by step
The order matters. Do it the other way around and you will send email before authentication is in place.
- Register the domain with a registrar you already use or trust. Turn on automatic renewal so the domain doesn't disappear if someone misses an invoice.
- Get an email service for the domain. It can be the same provider the company uses today, or a different one. What matters is that the domain has real inboxes and MX records, so that replies are received and the domain behaves like an ordinary email domain.
- Add SPF. This is a text record in DNS that states which servers may send email for the domain. A domain should have only one SPF record, otherwise it won't work.
- Enable DKIM. Your email service gives you a key that you add to DNS. It lets the recipient see that the email wasn't altered along the way.
- Create a DMARC record. Start with the policy none and an address where you receive reports. Once you have seen that everything legitimate gets through, you can tighten it.
- Send test emails to a few of your own addresses at different providers and inspect the email header. It shows whether SPF, DKIM and DMARC have passed.
- Warm up the inboxes before they are used for real.
Every domain has its own records. What is set up correctly on the main domain does not automatically apply here, and this is one of the most common mistakes. If SPF, DKIM and DMARC feel like a foreign language, there is a walkthrough for non-technical readers: SPF, DKIM and DMARC explained.
Warm-up takes time and can't be rushed. New domains have no history, and receiving systems see that as a warning flag in itself. How to ramp up without ending up in the spam folder is described in our article on email account warm-up.
How many inboxes do you need?
There is no magic number, but the principle is clear: many inboxes sending few emails each is better than a few inboxes sending a lot. It resembles ordinary human emailing, and if one inbox runs into trouble, the whole campaign isn't affected.
Two or three inboxes per domain works as a starting point. More than that on the same domain means a single bad week spreads to all of them. If you need more capacity, register another domain instead of packing more inboxes onto the first one.
Work backwards. Decide how many recipients you want to reach per week, divide by the number of working days, and then by the low daily limit you want to keep per inbox. The result is the number of inboxes, and therefore the number of domains. If the answer is unreasonably large for your company, it is often a sign that the target audience is too broad, not that you need more infrastructure.
Name the inboxes after real people: first name, last name, a reasonable signature. Don't send from info@ or sales@. The recipient should be able to reply to someone.
Here is how we do it ourselves: ModoLeads sends from its own domains that are warmed up in advance, with few emails per inbox per day, and the client's own domain and inboxes are not used. The same logic applies if you handle everything in-house. If you are weighing whether to hand over the whole job, including domains, warm-up and handling of replies, there is a description of how ModoLeads works. It is a choice, not a requirement.
What to keep track of afterwards
A domain isn't finished once it is set up. Look regularly at bounces, replies saying the address doesn't exist, and how many people mark the email as junk. If any of these increase, pause the inbox and look for the cause before you send more. The most common causes, and the order in which they tend to matter, are covered in Emails going to spam.
When someone replies and wants to talk, move the conversation to the company's regular address in the meeting invitation. That way the ongoing dialogue only reaches the main domain once the relationship is real.
Keep the email itself restrained too. A perfectly configured domain doesn't help if the text is a broadside to hundreds of different recipients. How to write emails that actually get replies is covered in B2B cold email.
When you don't need a separate sending domain
There are cases where it is unnecessary. If you send a handful of personal emails a week to people you have a concrete reason to contact, for example someone you have met or been referred to, it is in practice ordinary correspondence. The main domain is then enough, provided SPF, DKIM and DMARC are set up correctly.
The line is drawn at regularity and recipients who don't know you. When you start sending systematically to strangers, even in small volumes, it is time to separate the domains. It costs a domain fee and a little work. Losing deliverability on the main domain costs considerably more.
Start by opening an email you have sent from the main domain, look at the email header and check whether SPF, DKIM and DMARC show as passed. If you fix that first and register the second domain right afterwards, you will have the foundation in place before the first send.
Frequently asked questions
Can I use a subdomain instead of a domain of its own?
Yes, a subdomain is better than sending from the main domain. But reputation can carry over between a subdomain and the main domain, so a domain of its own is safer if cold email becomes an ongoing channel.
How many inboxes should I have per domain?
Two or three inboxes per domain is a reasonable starting point. If you need to reach more recipients, add a new domain instead of more inboxes on the same one.
Should the separate domain look like my company name?
Yes, the recipient should be able to recognize the sender. Use the company name with a short addition, and have the domain's web address redirect to your real website.