Email deliverability checklist for 2026: Gmail, Yahoo and Microsoft sender rules

If your emails land in spam, nothing else you do matters. Since 2024, the biggest mailbox providers have set clear rules for anyone who sends marketing email, and they enforce them. This checklist covers what is required, what is recommended and how to check you are compliant.

Who the rules apply to

Gmail and Yahoo introduced their bulk sender requirements in February 2024. Gmail applies the strictest ones to senders of about 5,000 or more emails a day to Gmail addresses, but the basics (authentication, low spam rates) apply to everyone. Microsoft added similar requirements for Outlook.com, Hotmail and Live addresses in 2025 for senders of more than 5,000 emails a day.

Even if you send less, follow them. They describe what every mailbox provider now expects.

1. Authenticate your domain

Send from your own domain (not a free Gmail or Yahoo address) and set up all three records:

• SPF: lists the servers allowed to send email for your domain.
• DKIM: adds a signature that proves the email wasn’t changed and came from your domain.
• DMARC: tells mailbox providers what to do with email that fails SPF or DKIM, and where to send reports. A policy of p=none is enough to meet the requirement; move to quarantine or reject once your reports look clean.

For bulk senders, the domain in your From address must also align with the domain that passes SPF or DKIM.

2. Make unsubscribing easy

Marketing emails must include:

• A visible unsubscribe link in the body.
• One-click unsubscribe headers (List-Unsubscribe and List-Unsubscribe-Post, defined in RFC 8058), so Gmail and Yahoo can show their own unsubscribe button.

Unsubscribe requests must be honoured within two days.

3. Keep spam complaints low

Spam complaints are the number that matters most.

• Stay under 0.3% of delivered emails reported as spam. That is the hard limit in Gmail’s and Yahoo’s rules.
• Aim for under 0.1%. Above that, your inbox placement already starts to suffer.

You can see your rate at Gmail in Google Postmaster Tools, which is free.

4. Keep your list clean

Most deliverability problems start with the list, not the content.

• Only email people who opted in. Never buy, rent or scrape lists.
• Use double opt-in for sign-ups from forms that attract fake or mistyped addresses.
• Remove hard bounces immediately. They tell providers you don’t maintain your list.
• Stop emailing people who haven’t opened or clicked in six months or so, or send them a re-engagement email first.

5. Send like a real business

• Send from a consistent name and address that people recognise.
• Keep a steady rhythm. Sudden large sends to an old list look like spam.
• Make sure your sending domain and IPs have reverse DNS (most sending services handle this).
• Use TLS for sending (every modern sending service does).

6. Check before you send

A quick pre-send check catches most problems:

• Is the domain authenticated and aligned?
• Is there a working unsubscribe link?
• Are the links on your own domain, without public link shorteners?
• Does the email have a sensible text-to-image balance and real text, not one big image?
• Did you send a test to Gmail and Outlook and check where it landed?

How SendCoop helps

• Domain setup: SendCoop gives you the SPF, DKIM and DMARC records for your sending domain and checks they are in place. Once a domain is verified, you can send from any address on it.
• Unsubscribe: every campaign includes an unsubscribe link and one-click unsubscribe headers.
• Bounces and complaints: hard bounces and spam complaints are recorded automatically, and those addresses are no longer emailed.
• Inbox score: check an email for common spam triggers before you send it.
• Account protection: if a list starts to bounce or generate complaints well above safe levels, sending pauses so the problem can be fixed before it damages your reputation.

The step-by-step guides are in the help docs: SPF, DKIM and DMARC explained and Verify your sending domain.