Cold email for B2B startups: how to get replies without landing in spam

For most B2B startups, the first customers don't arrive by themselves. Someone has to go and find them, and cold email is still one of the cheapest ways to start conversations with people who don't know you exist yet. It's also easy to do badly. Send generic emails to a big purchased list, and you'll get few replies, a damaged domain and possibly a legal problem.

Done well, cold email looks very different: a small list of companies you've chosen for a reason, a short first email about their situation, a couple of polite follow-ups, and a sending setup that inbox providers trust. This guide covers each part.

Is cold email legal?

In the US, yes. The CAN-SPAM Act doesn't require someone's permission before you send them a commercial email, and the FTC is explicit that it makes no exception for business-to-business email. Every commercial email must follow its rules:

• no false or misleading header information, so the "From" and routing must be accurate,
• no deceptive subject lines,
• identification of the message as an ad, where it is one,
• a valid physical postal address for your business,
• a clear way to opt out of future emails, and
• opt-outs honored within 10 business days, and never sold or shared.

You're also responsible for emails others send on your behalf, such as an agency. Each email that breaks the rules can cost up to $53,088 in penalties.

Other countries are stricter. Canada's anti-spam law and the rules in the UK and the European Union limit unsolicited email far more than CAN-SPAM does. If your list includes people outside the US, check the rules where they are before you send.

Choose who to email before you write anything

The biggest lever in cold email isn't the copy. It's the list. An average email to exactly the right person beats a brilliant email to the wrong one.

Start with a tight description of who buys from you:

• The company: industry, size, location and stage.
• The person: the role that feels the problem and can act on it.
• The trigger: a recent event that makes your product timely, such as a funding round, a new hire, a product launch or a job posting that suggests the problem.

Then build a list of perhaps 100 to 200 people who fit, not 5,000. A narrow list lets you research each company enough to write a relevant first line, and makes it obvious what's working. Our guide to building a B2B lead list covers where to find names and verified email addresses.

Write a first email that earns a reply

A cold email is read in a few seconds on a phone, by someone who didn't ask for it. Write for that.

• Open with them, not you. The first line should show why you chose this person: something specific about their company, role or recent news.
• Name the problem in their words. One or two sentences on the problem you solve, as they'd describe it.
• Give one piece of proof. A result for a similar company, a number or a relevant name, if you have it.
• Ask one easy question. "Is this worth a short call?" or "Who handles this on your team?" Not a 30-minute demo booked through a calendar link.
• Keep it short. Under about 100 words, in plain text, with no images or attachments and few or no links.

An example, for a startup that automates sales tax filing:

Subject: sales tax in 14 states

Hi Dana, I saw Northfield Supply started shipping to Canada and the West Coast this spring. Expanding like that usually means new sales tax registrations, and a filing calendar that's hard to keep straight by hand.

We file sales tax for about 40 online brands your size, so their teams don't spend a week a month on it.

Would it be worth a 15-minute call to see if it would help Northfield?

Sam

Follow up, politely

Many replies come from follow-ups, not the first email. Send two or three, a few days apart, each adding something new rather than "just bumping this."

• The second email: a short line in the same thread, perhaps with a different angle on the problem.
• The third email: a useful resource, such as a short case study or a relevant observation.
• The last one: a polite close, saying you won't follow up again, and asking if someone else would be better to talk to.

Stop as soon as someone replies or opts out, and never keep emailing someone who asked you to stop. That's a CAN-SPAM requirement, and it's basic courtesy.

Set up your sending so it reaches the inbox

The technical side of cold email decides whether anyone sees your message at all. Inbox providers judge each email partly on the reputation of the domain and mailbox that sent it.

Use a separate domain. Many teams send cold email from a domain close to their main one, such as getyourcompany.com instead of yourcompany.com, that redirects to the main website. If cold email harms the reputation of the secondary domain, your main domain, which carries invoices, customer support and password resets, isn't affected.

Authenticate it. Set up SPF, DKIM and DMARC on the sending domain. Google requires every sender to use SPF or DKIM, and senders of 5,000 or more emails a day to Gmail to use SPF, DKIM and DMARC, with the "From" domain aligned. Yahoo has the same bulk rules, and Microsoft began routing non-compliant mail from high-volume senders to junk from May 5, 2025. Our guide to setting up a domain for cold email walks through the records.

Warm it up. A new domain and mailbox have no reputation. Start with a few emails a day and increase over several weeks. Many cold email tools include automated warm-up.

Keep volume low per mailbox. Google Workspace allows up to 2,000 messages a day per user, but that's a technical limit, not a target. Experienced senders keep cold email to a few dozen a day per mailbox and add mailboxes to grow.

Keep complaints low. Google and Yahoo both say to keep spam complaint rates below 0.3%. Relevant emails to the right people, an easy opt-out and a clean list are what keep you there.

Keep your list clean

Bounced emails hurt your sender reputation. Before you send, verify every address with an email verification tool, and remove any that come back invalid or risky. Remove addresses that bounce during a campaign, and anyone who opts out, from every future campaign. Don't buy large lists of unknown origin. They are usually stale, and they're the fastest way to wreck a new domain.

Tools you'll need

A basic cold email setup has three parts.

• A data source to find companies, people and verified emails. Apollo combines a large B2B contact database with email sequencing and has a free plan. Our comparison of Apollo, Lusha and Hunter covers the options.
• Mailboxes on your secondary domain, usually through Google Workspace or Microsoft 365.
• A sending tool that schedules sequences, rotates mailboxes, handles warm-up and stops sequences when someone replies. Instantly's Growth plan costs $47 a month, or $37.60 a month billed annually, with unlimited email accounts and warm-up, 1,000 uploaded contacts and 5,000 emails a month. Our comparison of Instantly and Smartlead covers the two most common choices.

For a founder sending a few hundred emails a month, the total cost can be well under $100 a month.

Measure what matters

Track a few numbers for each campaign:

• Bounce rate. If it's more than a small fraction of sends, stop and clean the list.
• Reply rate, replies per hundred emails sent.
• Positive reply rate, the replies that lead to a conversation.
• Meetings booked and, eventually, customers.

Change one thing at a time, such as the list, the first line or the offer, and compare. Open rates are less reliable than they used to be, because some email apps load tracking pixels automatically, so don't steer by them.

Mistakes that sink cold email

• Sending to a huge, unfocused list. Low relevance means low replies and more spam complaints.
• Writing about yourself. The recipient cares about their problem, not your founding story.
• Asking for too much. A 30-minute demo is a big ask from a stranger. A short question is easier to answer.
• Sending from your main domain without authentication. One bad campaign can affect every email your business sends.
• Ignoring opt-outs. It's illegal, and it generates complaints.
• Scaling before it works. Get replies from 100 emails before sending 1,000.

What to do when someone replies

A reply is the start of a sale, not the end of the campaign. Answer within a few hours if you can. Move interested replies into your CRM so they don't get lost among sequences. Our guide to choosing a CRM for a startup covers the options. And treat "not now" replies kindly. Many become customers a few months later if you follow up when the timing changes.

How cold email fits with the rest of your sales

Cold email works best alongside other ways of reaching the same people, such as LinkedIn, referrals and content. It's especially useful early, when you're learning which customers care most about your product. The replies, and the objections, are research. Our guide to founder-led sales covers how to turn those first conversations into a repeatable process.