What is a cold email?

A cold email is an unsolicited email sent to a person you have no existing relationship with, for a business reason. No prior contact, no signup, no enquiry. You found them, decided they might have a problem you solve, and wrote to them.

That description also fits spam, which is why the distinction matters and why most explanations of it are unsatisfying. The honest answer is that the difference is not politeness or personalisation. It is whether the message is targeted, identifiable and honest about what it is.

Cold email versus spam

Spam is sent in bulk to addresses harvested or bought, with no reason to believe any particular recipient cares, usually hiding who sent it. A cold email goes to a specific person chosen because something about their role or company suggests relevance, from a sender who is easy to identify and easy to stop.

The practical test is whether you could explain to the recipient why they specifically received it. If the answer is that they were on a list, it is spam regardless of how well written it is.

• Targeted: chosen for a reason you could state out loud, not scraped in bulk.
• Identifiable: a real sender, a real company, a real reply address that a human reads.
• Honest: the subject line describes the message, and the message says what you want.
• Easy to end: an unsubscribe request is honoured the first time, permanently.

Is cold email legal?

In most jurisdictions, yes, for business to business mail, with conditions. CAN-SPAM in the United States permits unsolicited commercial email provided you identify yourself, use a truthful subject line, include a physical postal address and honour opt-outs promptly. It does not require prior consent.

GDPR in the EU and UK is stricter. It requires a lawful basis for processing personal data, which for B2B prospecting is usually legitimate interest, and that basis has to survive a balancing test against the recipient rights. CASL in Canada is stricter still and generally requires consent, with narrow exemptions. This is a summary rather than legal advice: the rules differ by country and by whether you are writing to an individual or a company.

Why most cold email is never seen

Legality is not the constraint most senders hit. Delivery is. A message that lands in the Junk folder was legal, well written and completely pointless, and this is the failure mode that surprises people arriving from content marketing.

Placement is decided before the recipient reads a word. The receiving mail system evaluates whether the sending domain is authenticated, whether it has a history, whether the volume looks human, and whether previous recipients engaged or complained. Copy quality matters only after that gate.

That is why the infrastructure side gets so much attention. Authentication is the entry requirement - SPF, DKIM and DMARC have been mandatory for bulk senders at Google and Yahoo since 2024 - and sending pattern is what keeps you there once you are in.

How cold email is actually sent

Nobody sends cold email from their main company mailbox, and this is the most common beginner mistake. If a sending domain accumulates complaints its reputation degrades, and if that domain is the one your invoices and support mail go out from, you have damaged the business to run a campaign.

1. Separate domains, similar to your brand but not your primary, registered specifically for sending.
2. A small number of mailboxes on each domain, each authenticated before first use.
3. A warmup period of two to four weeks so each mailbox builds a normal sending history.
4. A low daily volume per mailbox, with more mailboxes rather than more mail per mailbox.
5. A sequencer connected to those mailboxes, sending on a human-looking schedule.

The volume arithmetic follows from the last two points. If a Microsoft 365 mailbox safely sends three cold emails a day, reaching 300 a day means around 100 mailboxes rather than one mailbox working harder. Working out how many inboxes you need is usually the first real planning task.

What a cold email should contain

Short, specific, and about the recipient rather than about you. The opening line should make clear why you are writing to this person. The middle should describe a problem in their terms. The close should ask for one small, easy thing.

Avoid attachments, images and link shorteners in a first message. All three are heavily used in phishing, filters know it, and none of them earn their cost in a message whose only job is to start a conversation.

What to expect

A well targeted campaign with working infrastructure typically sees reply rates in the low single digits. That sounds discouraging until you multiply it out: a few hundred well chosen prospects a week is a steady flow of conversations. Rates far above that usually mean a very narrow list, and rates near zero usually mean a delivery problem rather than a copy problem.

If replies stop with no change to your copy or list, treat it as a placement issue first. The deliverability checklist covers the checks in the order that finds the cause fastest.