Cold email deliverability is the share of your cold emails that reach the inbox rather than the spam folder. It depends on four things: authenticated sending domains, a warmed sending history, a clean list, and emails people do not mark as spam.
Most deliverability guides are written for newsletters sent to people who opted in. Cold email is harder, because nobody asked for it, so the margins for error are smaller. This page covers the rules, the numbers and the fixes for cold email specifically. For the full setup, start with our guide to cold email for agencies.
What is cold email deliverability?
Cold email deliverability is whether your outreach lands where the prospect will actually see it. An email can be "delivered" in the technical sense and still be useless, because it went to spam or to a tab the reader never opens.
There are three outcomes for every message:
- Rejected. The receiving server refuses it, and you get a bounce.
- Delivered to spam. The server accepts it and files it as junk. You get no error, and usually no reply.
- Delivered to the inbox. The prospect sees it. In Gmail, a message in the Promotions tab is technically in the inbox but often goes unread.
Deliverability is the work of moving as many messages as possible into the last group.
Why are my cold emails going to spam?
Cold emails usually go to spam because of one of six causes. Most problems trace back to the setup, not the wording.
| Cause | What the filter sees | The fix |
|---|---|---|
| Missing or broken authentication | Mail it cannot verify came from you | Publish SPF, DKIM and DMARC and check they pass |
| No sending history | A brand-new mailbox sending to strangers | Warm up for at least 14 days before cold sending |
| Too much volume | A sudden spike from one mailbox or domain | Cap at 30 cold emails per mailbox per day, 2 mailboxes per domain |
| A dirty list | Bounces from addresses that do not exist | Verify every address before sending |
| Spam complaints | Readers pressing "report spam" | Target tightly, write relevant emails, make opting out easy |
| Content that looks like marketing | Tracking links, images, attachments, sales language | Plain text, few or no links, no attachments in the first email |
Content matters less than most people think. A perfectly written email from an unauthenticated, brand-new domain will still land in spam. Fix the setup first, then the words. If it is already happening to you, our page on why cold emails go to spam walks through the diagnosis step by step.
What do Gmail, Yahoo and Outlook require from cold email senders?
Gmail, Yahoo and Outlook all require authenticated mail and low spam complaints, with stricter rules for anyone sending more than 5,000 messages a day. Gmail and Yahoo began enforcing their rules in February 2024, and Microsoft followed for Outlook.com in May 2025.
| Requirement | Gmail | Yahoo | Outlook.com |
|---|---|---|---|
| SPF or DKIM, all senders | Required | Required | Recommended |
| SPF and DKIM and DMARC (p=none or stricter), high-volume senders | Required above 5,000 a day | Required for bulk senders | Required above 5,000 a day |
| Spam complaint rate | Below 0.3% | Below 0.3% | Not published as a number |
| One-click unsubscribe | Required for bulk marketing mail | Required for bulk senders | Not published |
| Valid forward and reverse DNS for sending servers | Required | Required | Not published |
Sources: Google's email sender guidelines, Yahoo's sender requirements, and Microsoft's announcement for high-volume senders.
Two practical points follow. First, a well-run cold email setup sends far below 5,000 a day per domain, but you should meet the stricter rules anyway: they are what good senders look like. Second, the 0.3% complaint line is a ceiling, not a target. Google's guidelines ask senders to stay below 0.1% and never reach 0.3%.
Which cold email deliverability numbers should you watch?
Watch four numbers on every mailbox and domain: bounce rate, spam complaint rate, warm-up spam rate, and reply rate. The first three tell you about reputation before the fourth starts to fall.
| Metric | What it measures | Healthy | Act at |
|---|---|---|---|
| Bounce rate | Share of sends rejected as undeliverable | Under 2% | 3%: pause and clean the list |
| Spam complaint rate | Share of recipients who report the email as spam | As close to 0% as possible | 0.1%: pause and review targeting |
| Warm-up spam rate | Share of warm-up emails that land in spam, over 7 days | Under 10% | 20%: take the mailbox off cold email |
| Reply rate | Share of prospects who reply | Steady week to week | A sudden drop with steady sends |
Our cold email bounce rate guide explains how to calculate the first number and what to do when it spikes.
The bounce and complaint lines are the points where Pipefire pauses a campaign automatically. The warm-up line is where it takes a mailbox off cold sending and back into warm-up. Our email warm-up guide explains how that rate is measured and why it is the earliest warning you get.
A sudden fall in replies with no change in volume often means mail has started going to spam. It is the last signal to arrive, so do not rely on it alone.
Reputation is the score behind most of this: see sender reputation for cold email, and how to watch Gmail's view of it in our Google Postmaster Tools guide.
Start with our cold email deliverability checklist, then see how Gmail's spam filter decides.
How do you test cold email deliverability?
Test deliverability by sending real emails to mailboxes you control at Gmail and Outlook, then checking which folder each one landed in. This is called an inbox placement test, and it is the only direct measurement of where your mail goes. Our cold email deliverability test guide covers every method, and how to calculate an inbox placement rate. For quick free checks you can run in five minutes, see how to check if your cold emails go to spam.
A useful test follows four rules:
- Use real provider accounts. Send to genuine Gmail and Microsoft 365 or Outlook.com mailboxes, not to another mailbox on your own sending setup.
- Send the real email. Test the actual subject line and body you plan to send, from the actual mailbox.
- Check the Gmail tab as well as the folder. A Gmail message in Promotions counts as "inbox" to most tools that connect over IMAP, but the prospect may never see it. Read the Gmail labels or look in the account directly.
- Repeat it. One test is a snapshot. Test again after changes and every few weeks while a campaign runs.
For a quick free check, send one email to a Gmail address you own, open it, and choose "Show original". Gmail shows whether SPF, DKIM and DMARC passed. If any says anything other than "PASS", fix that before testing anything else.
Paid placement tools run this for you across dozens of providers at once, and most sending platforms include a basic version. Whichever you use, check that it reads Gmail tabs and that its test accounts are real outside mailboxes.
A free header check answers one question: did this message pass authentication right now. A paid placement tool answers a different one: where is a whole campaign landing across dozens of providers, tracked over weeks. Run the free check first, on every new domain, before paying for anything.
Be careful with tests that only send between your own mailboxes. They almost always show 100% inbox, because your own setup trusts itself. That result tells you very little about how Gmail or Outlook will treat a stranger's copy.
Our guide to inbox placement explains the metric itself and its limits, and our guide to cold email deliverability tools maps which tool measures what.
How do you improve cold email deliverability?
Improve cold email deliverability by fixing the setup in order: domains, authentication, warm-up, volume, list, then content. Each step depends on the one before it.
- Send from separate domains. Never your main domain. Our guide to cold email domains covers naming and setup.
- Authenticate every domain. SPF, DKIM and DMARC, all passing, checked in the message headers. Our SPF, DKIM and DMARC guide has the exact records.
- Use a mainstream mail provider. Google Workspace or Microsoft 365 mailboxes start with the provider's reputation behind them.
- Warm up for at least 14 days. Then ramp cold volume from about 5 a day to 30 over the next two weeks.
- Cap volume. At most 30 cold emails per mailbox per weekday, and 2 mailboxes per domain. Our cold email mailboxes guide shows how many you need for your volume.
- Verify every address. Keep bounces under 3%, and preferably under 2%. Our cold email list quality guide explains catch-all addresses, spam traps and how to verify a list.
- Target tightly. Email the person who owns the problem you solve. Relevant emails get fewer complaints and more replies.
- Write plain emails. Short, plain text, about the prospect's business, with no tracking images, attachments or link shorteners.
- Make opting out easy. A clear way to say no keeps people from pressing "report spam" instead.
- Keep warm-up running and watch the numbers. Pause anything that crosses a line, the same day.
None of these is a trick. Inbox providers reward senders who look like careful people, and punish senders who look like bulk mailers. Every item above makes you look like the first kind.
How do you fix a cold email sending domain that is landing in spam?
Stop cold sending from it straight away, find the cause, and decide whether to rest it or replace it. Keep the rest of your domains sending; one bad domain should not stop the campaign.
Work through the likely causes in order:
- Authentication. Check SPF, DKIM and DMARC still pass. A DNS change elsewhere can quietly break a record.
- Volume. Check whether any mailbox on the domain sent more than its usual daily limit.
- The list. Check the bounce rate on recent sends. A batch of bad addresses is a common trigger.
- Complaints. Check whether one segment or one email drew more complaints than the rest.
Once the cause is fixed, put the domain back on warm-up only. If its warm-up mail returns to the inbox, restart cold sending at about 5 a day and ramp up again. If it does not recover within a few weeks, retire it. A replacement domain costs about $11, and a warm spare can take its place at once.
Pipefire runs these checks and pauses on every mailbox automatically. Our deliverability page shows how the product applies each threshold, and health checks explains what happens to a mailbox that crosses one.
Cold email deliverability FAQ
What is a good email deliverability rate for cold email?
Aim for almost all mail to reach the inbox, with bounces under 2% and spam complaints close to zero. Measure placement with real Gmail and Outlook test accounts rather than trusting a single score. Our guide to a good cold email deliverability rate explains why most published figures measure delivery, not inbox placement.
Why are my cold emails going to spam in Gmail?
The usual causes are missing SPF, DKIM or DMARC, a new mailbox with no warm-up, too many emails from one mailbox, or bounces from a bad list. Check the message headers with "Show original" first.
Does Gmail's 5,000 a day rule apply to cold email?
The stricter rules apply above 5,000 messages a day to Gmail accounts. Most cold email setups send far less per domain, but meeting the stricter rules anyway is the safer choice.
How long does it take to fix cold email deliverability?
Fixing a setup problem such as a broken DNS record takes minutes. Rebuilding a damaged domain's reputation takes weeks of warm-up, and sometimes replacing the domain is faster.
Do links in cold outreach emails hurt deliverability?
Links can. Tracking links, link shorteners and several links in one email all look like marketing. Use no links in the first email, or one plain link to your own site.
What is an inbox placement test for cold email?
An inbox placement test sends your real email to test accounts at Gmail, Outlook and other providers, then reports which folder or tab each copy landed in. It is the most direct measure of deliverability.