A recurring question with a genuinely two-sided answer: should cold email go out from mail.yourcompany.com, or from a separate domain like getyourcompany.com?
The appeal of the subdomain is obvious. It carries your real brand, prospects who look it up find your actual company, and it inherits some of your established domain’s standing.
The problem is that inheritance is not one-directional.
How subdomain reputation actually works
Three things are true at once, which is why the question is confusing.
Subdomains have their own reputation. Providers score mail.company.com separately from company.com. A new subdomain starts with little history of its own.
But not entirely separately. Signals propagate between a root domain and its subdomains. A subdomain inherits some standing from an established root, and, this is the part that matters, a badly-behaved subdomain can affect how the root is treated.
The degree is not published. Providers do not document how strongly the two are linked, and it differs between Gmail, Microsoft and corporate gateways. Anyone claiming a precise ratio is guessing.
So the honest summary: a subdomain is not a firewall. It is a partition with some leakage, and you cannot measure the leak.
When a subdomain makes sense
Transactional and marketing mail. This is the textbook use and it is sound. mail.company.com for newsletters, notify.company.com for product emails. Known recipients, low complaint risk, and the brand association is a benefit.
Warm outbound to existing relationships. Re-engaging past customers, event follow-up, conversations that started elsewhere. Complaint risk is low and the recognisable domain helps.
Low-volume, high-value outreach. Twenty carefully researched emails a month to named enterprise accounts. At that volume and care level the risk is small and the credibility matters.
When the brand is the pitch. If your prospects already know your company, an unfamiliar domain costs you more than it protects.
When it does not
Cold email at volume. The core case, and the answer is no.
Cold outreach generates complaints. Not because you are doing it badly, because some proportion of people who did not ask to hear from you will mark it as spam regardless. At 2,000 sends a month, even a good complaint rate produces complaints.
Those complaints attach to the subdomain, and some portion of that signal reaches the root. The root domain is where your invoices, your support replies, your password resets and your customer conversations originate. Risking it to save the cost of a separate domain is a poor trade when separate domains cost a few dollars a year.
When you need many sending domains. A real cold email estate uses three mailboxes per domain across many domains, to spread risk and volume. Doing that with subdomains means mail1., mail2., mail3., which looks exactly like what it is, and concentrates all of them under one root.
When you are rotating or retiring domains. A separate domain that becomes damaged gets retired for $6. A damaged subdomain is attached to your company’s root forever.
The decision
| Your situation | Use |
|---|---|
| Newsletters, transactional mail | Subdomain |
| Warm follow-up to known contacts | Subdomain |
| Under ~50 cold emails a month to named accounts | Subdomain, carefully |
| Cold email at any real volume | Separate domains |
| Multiple sending domains needed | Separate domains |
| Agency sending on behalf of clients | Separate domains, in the client’s name |
The threshold is not precisely findable, but the principle is: if the mail will generate complaints from people who do not know you, keep it off anything connected to your primary domain.
What separate domains should look like
Covered fully in buying domains for cold email, but the short version since it is the recommendation here:
Plausible variants of your brand. getnorthgate.com, trynorthgate.com, northgatehq.com. Not numbered, not random.
A real TLD. .com first; .co and .net fine. Avoid the cheap TLDs spam volume has poisoned.
Something at the root. A redirect to your main site, or a simple page. A domain with no web presence is a small negative signal and takes minutes to fix.
Three mailboxes each, five maximum.
Full authentication, verified rather than assumed.
Prospects who look you up will find a page that makes sense and connects to your real company. That is most of the credibility a subdomain would have given you, without the shared risk.
The hybrid that works
Many teams land here and it is a sensible place.
Primary domain, never sends cold mail. Website, invoices, support, customer conversations.
Subdomain of the primary, transactional and marketing mail to known contacts.
Separate outreach domains, all cold email, rotated and replaced as needed.
Three tiers, each carrying a different risk profile, and a problem in the third cannot reach the first.
The short version
Subdomains have their own reputation and also share signal with the root. That makes them right for mail to people who know you and wrong for mail to people who do not.
Cold email generates complaints by its nature. Those complaints should land somewhere disposable, not on a subdomain of the domain your business runs on.
Use subdomains for newsletters, transactional mail and warm follow-up. Use separate, plausible, properly authenticated domains for cold outreach, they cost a few dollars a year and they can be retired when damaged, which a subdomain of your company cannot.
Next: buying domains for cold email, or what sender reputation is.
Frequently asked questions
Should I use a subdomain for cold email?
Not for cold email at volume. Subdomains share reputation signal with the root domain, and cold outreach generates complaints by nature. Use separate domains that can be retired if damaged.
Do subdomains have separate reputation from the root domain?
Partly. Providers score subdomains separately but signal propagates in both directions, and the degree is not published. A subdomain is a partition with leakage rather than a firewall.
What should I use a sending subdomain for?
Transactional mail, newsletters and warm follow-up to people who know you, anything where complaint risk is low and brand recognition helps.
Is it safe to send marketing email from mail.mydomain.com?
Yes, for mail to known contacts who expect it. The risk comes from cold outreach, where complaints from people who did not ask to hear from you can affect how the root domain is treated.