David Roberts
Founder and CEO
10.13.2026
Emails usually land in spam for one of four reasons: the sending domain is not properly authenticated with SPF, DKIM and DMARC; too many recipients mark the mail as spam; the list contains invalid, old or unengaged addresses; or the content and sending patterns look like bulk spam. Since 2024, Gmail and Yahoo have required bulk senders to authenticate their mail, offer one-click unsubscribe and keep spam complaint rates below 0.3%, and Microsoft began enforcing similar rules for Outlook.com, Hotmail and Live addresses in 2025.
Deliverability means getting into the inbox, not just getting accepted by the receiving server. A message can be “delivered” and still be sent straight to spam. This guide explains how mailbox providers decide where your email goes, the current sender requirements and a step-by-step checklist to fix spam-folder problems.
In This Guide
Why Do Emails Go To Spam?
| Cause |
What Mailbox Providers See |
| Missing or broken authentication |
No proof the message really comes from your domain |
| High spam complaints |
Recipients do not want your mail |
| Poor list quality |
Bounces, spam traps and inactive addresses signal bad list practices |
| Low engagement |
Few opens, replies or clicks; many deletions without reading |
| Sudden volume spikes |
A new or quiet domain suddenly sending thousands of messages |
| Hard-to-find unsubscribe |
Recipients use the spam button instead |
| Suspicious content or links |
Link shorteners, mismatched domains, image-only emails, misleading subject lines |
| Shared IP or domain reputation |
Other senders on the same infrastructure behaving badly |
Reputation is the thread running through all of these. Mailbox providers score both your sending domain and your sending IP addresses based on how recipients react to your mail over time.
What Are The Gmail, Yahoo And Microsoft Sender Requirements?
Google and Yahoo announced new bulk sender rules in October 2023, with enforcement starting in February 2024. Microsoft followed for its consumer domains in 2025, according to dmarcian. A bulk sender is generally anyone sending around 5,000 or more messages a day to that provider’s personal accounts.
| Requirement |
Gmail |
Yahoo |
Microsoft (Outlook.com, Hotmail, Live) |
| SPF and DKIM |
Required for bulk senders |
Required for bulk senders |
Required for high-volume senders |
| DMARC record |
Required (p=none minimum) |
Required (p=none minimum) |
Required (p=none minimum) |
| Alignment with From domain |
Required |
Required |
Required |
| One-click unsubscribe (marketing mail) |
Required |
Required |
Recommended |
| Spam complaint rate |
Below 0.3%; aim for under 0.1% |
Below 0.3% |
Keep low; no public threshold |
| Valid reverse DNS and TLS |
Required |
Required |
Expected |
Even if you send far fewer than 5,000 emails a day, follow these rules. Smaller senders are judged by the same signals, just with less volume to go on. A 0.3% complaint rate means about three spam reports per 1,000 delivered messages, which is easy to exceed with a poorly targeted list.
How Do SPF, DKIM And DMARC Work?
| Record |
What It Does |
Common Mistake |
| SPF |
Lists the servers allowed to send mail for your domain |
Forgetting to add a new email tool, or exceeding the 10 DNS lookup limit |
| DKIM |
Adds a cryptographic signature proving the message was not altered and came from your domain |
Each sending platform needs its own DKIM key set up; many teams set up only one |
| DMARC |
Tells providers what to do if SPF or DKIM fails, and sends you reports |
Publishing p=none and never reading the reports or moving to a stricter policy |
Start DMARC at p=none to collect reports, find every legitimate service sending as your domain, fix their authentication, then move gradually to p=quarantine and p=reject to stop spoofing.
How Do You Fix Emails Going To Spam? A 10-Step Checklist
- Authenticate every sending source. Set up SPF, DKIM and DMARC for your domain and for every platform that sends on your behalf: email marketing tool, CRM, help desk and transactional email service.
- Send from your own domain. Never send bulk mail from a free address like @gmail.com through a third-party tool; it will fail DMARC.
- Separate mail streams. Use a subdomain for marketing (for example, news.yourdomain.com) so a campaign problem does not damage delivery of invoices and password resets.
- Clean your list. Remove hard bounces immediately, suppress addresses that have not engaged in several months and never buy lists.
- Use confirmed opt-in for new signups. It keeps typos, bots and spam traps off your list.
- Add one-click unsubscribe and honor it quickly. Yahoo expects unsubscribes to be processed within two days. An easy exit lowers spam complaints.
- Warm up new domains and IPs. Start with small volumes to your most engaged contacts and increase gradually over several weeks.
- Write for people, not filters. Clear sender names, honest subject lines, a balanced text-to-image ratio and links to your own domain.
- Send what people expect. Match frequency and content to what subscribers signed up for. Unexpected mail generates complaints.
- Monitor and adjust weekly. Watch complaint rates, bounces and inbox placement, and pause any campaign that spikes complaints.
How Do You Monitor Deliverability?
- Google Postmaster Tools: shows spam rate, domain reputation and authentication results for Gmail traffic.
- Yahoo Complaint Feedback Loop: reports complaints from Yahoo users.
- Microsoft SNDS: provides data on IP reputation for Outlook.com traffic.
- DMARC reports: show who is sending as your domain and whether they pass authentication. A DMARC reporting tool makes these readable.
- Inbox placement tests: seed tests show whether messages land in inbox, promotions or spam across providers.
Pick an email platform with strong deliverability tooling. Our roundup of the best SMTP services in 2026 compares options for transactional and bulk sending.
Does Cold Email Follow Different Rules?
Cold outreach faces the same filters, with fewer engagement signals to help. To protect your main domain, many teams send cold email from a separate, properly authenticated domain, keep daily volumes per inbox low, personalize every message and stop sending to anyone who does not respond after a short sequence. Also check the laws that apply where your recipients are, such as CAN-SPAM in the US, CASL in Canada and GDPR and related rules in the EU and UK.
Frequently Asked Questions
Why are my emails going to spam in Gmail but not Outlook?
Each provider weighs signals differently. Gmail puts heavy weight on engagement and complaint rates. Check Google Postmaster Tools for your spam rate and domain reputation.
Do the Gmail and Yahoo rules apply to small senders?
The strict bulk requirements apply at around 5,000 daily messages, but every sender needs at least SPF or DKIM, valid DNS and a low spam rate. Following the full set of rules improves inbox placement at any volume.
How long does it take to fix a bad sender reputation?
Usually several weeks of consistent, clean sending to engaged recipients. Google considers mitigation only after spam rates have stayed below 0.3% for a sustained period.
Does landing in the Promotions tab count as spam?
No. Promotions is still the inbox. It may reduce opens, but it does not harm your reputation the way spam placement does.
The Short Version
Authenticate every sending source with SPF, DKIM and DMARC, send from your own domain, offer one-click unsubscribe, keep spam complaints under 0.3% and ideally under 0.1%, clean your list regularly and warm up new domains slowly. Monitor Google Postmaster Tools and DMARC reports every week, and pause any campaign that drives complaints up. For the wider security picture, see our small business cybersecurity checklist.
