Cold email is the engine of link building and the fastest way to burn a sending domain. Both facts follow from the same property: it is cheap to send and expensive to send badly. The difference between a programme that runs for years and one that dies in six weeks is almost entirely operational.
Start with the rules, because they are not optional
Commercial email is regulated in most markets you will be sending to. In practice that means: do not disguise who you are, use a real reply-to address, make the sender's identity accurate, honour opt-out requests immediately and permanently, and check the requirements in the recipient's jurisdiction rather than yours.
Beyond compliance, one operational rule matters more than any tactic: honour "please don't contact me again" as permanent, across every campaign, forever. A suppression list that resets between campaigns is how a small niche learns your name for the wrong reason.
The list is the whole thing
Bad lists cause bad deliverability, and bad deliverability is not recoverable in a week. Before any campaign, every prospect should pass: the site is topically relevant, it publishes regularly, it links out to independent sources, and there is a specific page where your link would genuinely belong.
Verify the addresses. A campaign to a list with a high invalid rate can put a sending domain in trouble that takes weeks to undo, which is the most expensive kind of mistake because it stops everything else too.
Sending limits are lower than you think
| Setting | Sensible | Risky |
|---|---|---|
| Per mailbox per day | Around 40 | 150+ |
| New domain warm-up | Weeks, ramping slowly | Full volume on day one |
| Invalid address rate | Under 2% | Over 5% |
| Identical message bodies | Never | Merge fields only |
| Links per email | One | Three or more |
Use a subdomain for outreach rather than your primary domain, so a problem does not take your business email with it. Set up authentication properly before the first send — this is a one-hour task that prevents a category of failure you otherwise cannot diagnose.
What to write
One sentence per email must be impossible to send to anyone else, and it is usually the second. Name their page, quote a line, identify the exact paragraph where your resource belongs. Everything else can follow a consistent structure.
Keep the ask small enough to refuse easily. "Is this the sort of thing you'd want there, or not a fit?" gets answered more often than "would you link to this?", because "not a fit" is a comfortable reply to send. The structures are in the templates guide, and the full sequence in the outreach guide.
Follow up twice, then stop
Most placements arrive after the first follow-up. Almost none arrive after the third. Two touches after the initial email, each adding something new, then a clean close — that is the whole cadence, and extending it trades a negligible gain for a real cost in reputation.
The signals that mean stop sending
Reply rate collapsing across a campaign that was working. Bounce rate climbing above a couple of percent. Replies arriving from people who clearly did not understand why you contacted them. Any spam complaint at all.
Each of these means the list or the targeting has drifted, and sending more will make it worse rather than better. Pause, re-verify, re-filter, and restart at lower volume. The instinct to push through is the one that costs a domain.
Where the tooling helps and where it does not
Software should carry verification, sending limits, suppression, reply detection and the record of who said what. It should not write the sentence that proves you read their site — that is the part being evaluated, and automating it is what produced the reputation cold email currently has. Our email outreach tooling handles the operational half, and the outreach CRM keeps replies from being lost.
Frequently asked questions
Is cold email legal for link building?
In most markets, business-to-business cold email is legal provided you identify yourself honestly, use a genuine reply address, and honour opt-out requests promptly. Requirements differ by jurisdiction and some are stricter about prior consent, so check the rules where your recipients are rather than where you are. Honouring opt-outs permanently is both a legal requirement and basic practice.
How many cold emails can I send per day safely?
Around forty per mailbox, with genuine variation between messages, keeps you inside normal sending behaviour. A new domain needs a slower ramp over several weeks before reaching that. Volume is rarely the constraint that matters — a well-filtered list of 200 prospects will outperform 2,000 poor ones without putting your domain at risk.
Why is my cold outreach going to spam?
The most common causes are missing or misconfigured email authentication, a new domain sent at full volume immediately, a high invalid-address rate from an unverified list, and near-identical message bodies across a large send. Authentication and list verification fix the majority of cases; if reply rates were fine and then collapsed, look at the list first.
How do I improve cold email reply rates?
Improve the list before touching the copy. Most low reply rates come from contacting sites that had no reason to be interested, not from the wording. Once the list is genuinely filtered, the highest-return change is making the second sentence specific enough that it could not have been sent to anyone else.