Cold email deliverability: a founder’s checklist

Use separate sending domains

Never send cold email from the domain your business runs on. Register one or more similar domains (for example, a variation of your brand name) and point them to your main site. If a sending domain gets a bad reputation, your main domain stays clean.

Use more than one inbox per sending domain only within sensible limits, and spread volume across them.

How to pick a sending domain

Choose a domain that is clearly related to your brand, so a reader who checks it is not confused. Common patterns are your brand name with a short word added, such as “get”, “try” or “team”, or the same name on a different ending. Avoid names that look like a misspelling of a big company; they read as phishing.

Then do three things before any email goes out:

1. Redirect the website of the sending domain to your main site, so a curious reader lands somewhere real.
2. Create real mailboxes with real names, like the founder’s first name.
3. Give the domain time. A domain registered yesterday is a warning sign to filters. Set it up early and let it age while you warm up the inboxes.

How many domains and inboxes

Start small: one sending domain and one or two inboxes is enough for a founder sending a few dozen personal emails a day. Add more only when you need more volume, and spread the volume evenly. More inboxes do not fix a bad message; they only spread the damage.

A simple capacity check (illustrative)

Before you buy domains, work backward from the number of people you actually want to reach. But don’t start from a big number you saw in someone’s screenshot. So use your own goal.

Say you want to reach 200 new people a month, with a first email and two follow-ups. That is up to 600 emails a month, or about 30 per working day. Spread across four inboxes, each sends fewer than ten a day. That is a calm, safe pace for warmed-up inboxes. The numbers are illustrative; check the daily limits your own sending tool recommends.

If your goal needs far more than that, the answer is rarely “more domains”. It is usually a better list, so fewer emails produce more replies.

Keep your main domain clean

Your main domain carries invoices, customer replies and password resets. But many founders forget that a single noisy campaign from it can push those emails into spam too. So keep a few habits:

• Send cold email only from sending domains.
• Keep your main domain’s DMARC, SPF and DKIM set up as well, even if you never send outreach from it.
• Don’t put links to the sending domain inside customer emails; link to your main site instead.
• When someone replies with interest, continue the conversation from your main inbox if that feels natural, and tell them so.

Authenticate every domain

Three DNS records tell receiving servers your email is legitimate:

• SPF: lists which servers may send for your domain.
• DKIM: adds a signature that proves the email wasn’t changed.
• DMARC: tells receivers what to do when SPF or DKIM fails, and where to send reports.

Major mailbox providers now expect all three for bulk senders. Set them up before you send anything.

What Google and Yahoo require

Since February 2024, Google and Yahoo have required bulk senders (those sending 5,000 or more messages a day to their users) to meet a set of rules, summarized in the Close help center:

• SPF, DKIM and DMARC must all be set up. DMARC must be published at least at p=none.
• Alignment: the domain in the From address must match the SPF or DKIM domain.
• Spam rate must stay below 0.3%, and below 0.1% is considered healthy.
• One-click unsubscribe is required for promotional messages.
• Yahoo expects unsubscribes to be honored within 2 days.

A founder sending 30 emails a day is far below the 5,000 line. But these rules show what filters reward, and a setup that passes them is a setup that lands in the inbox. So treat them as the standard from day one.

Setting up the records, step by step

1. Find your DNS settings at the company where you bought the domain, or wherever your DNS is hosted.
2. Add the SPF record your email provider gives you. One SPF record per domain; if a tool asks for another, merge it into the same record.
3. Turn on DKIM in your email provider’s admin panel and add the record it shows you.
4. Add a DMARC record starting at p=none, with an address that receives reports.
5. Test. Send an email to a mailbox you control and check the message headers, or use a free DNS checker, to confirm SPF, DKIM and DMARC all pass.
6. Tighten DMARC later. Once reports show your legitimate email passes, move from p=none to p=quarantine, then to p=reject.

Warm up and ramp slowly

A brand-new inbox that suddenly sends hundreds of emails looks like spam. Start with a small number of emails per day and increase gradually over several weeks. Many sending tools include automatic warm-up; use it, but don’t treat it as a free pass for high volume.

What a careful ramp-up looks like

Think in weeks, not days. In the first week, send only a handful of real emails a day to people likely to reply. In the following weeks, increase slowly while you watch bounces and complaints. Exact numbers vary by provider and tool, and they change, so follow the current limits your sending tool recommends.

Replies are the best signal you can give a mailbox provider. But you can’t fake them for long. So warm-up works best when the first real emails go to warm contacts: past customers, friendly prospects, people who already know you.

A worked setup: from zero to first real send

Founders often ask what a careful setup looks like on a calendar. But every tool and provider is a little different. So treat the plan below as an illustrative shape, not a fixed schedule, and confirm exact warm-up volumes with your sending tool.

The point of the plan is patience at the start. A domain that goes from zero to hundreds of emails in a day looks like a spammer. A domain that grows slowly looks like a business.

How to check that authentication works

You don’t need special tools for a first check:

1. Send an email from your new inbox to a personal Gmail account.
2. Open it, then open the menu and choose “Show original”.
3. Look for SPF, DKIM and DMARC. Each should say “PASS”.
4. Repeat with an Outlook address if your buyers use Microsoft email.

If any line says “FAIL” or is missing, fix the DNS record before you send anything real. DNS changes can take time to spread, so check again after a few hours.

Watch blocklists and IP reputation

If your emails suddenly stop arriving, check whether your sending domain or IP is on a blocklist. Services like Microsoft and Proofpoint maintain their own lists and have delisting forms.

What to do when you’re blocked

1. Stop sending from the affected domain or IP. Every new email makes the record worse.
2. Find the source. Look at bounce messages; they usually name the filter or list.
3. Fix the cause: a bad list, a sudden volume jump, a spammy message, or missing authentication.
4. Request delisting through the provider’s official form, and explain what you changed.
5. Restart slowly, with your best contacts first, and watch the numbers daily for two weeks.

Troubleshooting: what the symptom tells you

Deliverability problems rarely announce themselves. But each symptom points to a different cause. So match what you see to the likely cause before you change anything.

Write down what you changed and when. Deliverability problems often show up a few days after the cause, so a simple log saves hours of guessing.

Monitor three numbers

When bounces or complaints rise, pause the campaign. Sending more makes it worse.

For spam complaints, the bulk-sender rules give a clear line: stay below 0.3%, and aim for below 0.1%. At founder volumes, even two or three complaints in a small batch are a strong signal to stop and rewrite.

What a healthy week looks like (illustrative)

A healthy setup is boring. Week after week, bounces stay low, complaints stay near zero, and replies keep coming at a steady rate. But boring is the goal. So watch for any change, not for any single number.

If one week shows a jump in bounces after a new list, the list is the cause. If replies drop while nothing else changed, test the inbox placement. If complaints appear after a new template, the template is the cause. Change one thing, wait a week, and compare.

Write like a person

Deliverability is not only technical. Short plain-text emails, no tracking-heavy links, no attachments in the first email, and a real reason to write all help.

Common deliverability mistakes

1. Sending from the main domain: the most expensive mistake, because it affects every customer email.
2. Buying a list: old and guessed addresses bounce, and bounces damage reputation fast.
3. Skipping verification: even a list you built yourself has typos and dead addresses.
4. Big jumps in volume: going from 20 a day to 500 overnight looks like a compromised account.
5. Images, attachments and many links in the first email: they look like marketing to filters.
6. Ignoring opt-outs: it is a legal problem and a reputation problem at once.
7. Fixing copy when the problem is delivery: if replies drop suddenly, check placement before rewriting.

A weekly 10-minute routine

Once a week:

1. Check bounce, complaint and reply rates per inbox.
2. Send a test email to a Gmail and an Outlook address you own and see where it lands.
3. Remove bounced and opted-out contacts from every list.
4. Look at DMARC reports for anything failing.
5. If one inbox looks worse than the others, pause it and find out why.

This takes less time than writing one email. It protects every email you send after it.

Deliverability terms in plain English

• Deliverability: whether your email reaches the inbox, not just whether it was sent.
• Sending domain: a domain you use only for outreach, separate from your main business domain.
• SPF: a DNS record that lists which servers may send email for your domain.
• DKIM: a digital signature that proves an email really came from your domain and wasn’t changed.
• DMARC: a DNS record that tells receivers what to do when SPF or DKIM fails, and where to send reports.
• Alignment: the “From” domain matches the domain checked by SPF or DKIM.
• Warm-up: slowly increasing sending volume so mailbox providers learn to trust a new inbox.
• Bounce: an email that could not be delivered. A hard bounce means the address doesn’t exist.
• Spam complaint: a recipient marking your email as spam. This hurts more than a bounce.
• Blocklist: a list of domains or IP addresses that some providers refuse to accept mail from.
• Reputation: how much mailbox providers trust your domain and IP, based on past behavior.

What to do this week

1. Today: list every domain you send from. If cold email goes out from your main domain, stop and plan a separate one.
2. Tomorrow: check SPF, DKIM and DMARC with the “Show original” test above.
3. This week: turn on warm-up for any inbox younger than a few weeks.
4. Friday: write down this week’s bounce, complaint and reply numbers. That is your baseline.
5. Every Friday after: compare with the baseline and act on any rise in bounces or complaints.

The checklist

• Separate sending domain(s), not your main domain
• SPF, DKIM and DMARC set on each sending domain
• Inboxes warmed up over several weeks
• Daily volume per inbox kept modest
• List verified before sending
• Unsubscribe or opt-out honored
• Bounce, complaint and reply rates checked weekly
• Blocklist check when results drop suddenly

Questions and answers