Gmail, Yahoo and Microsoft sender rules: what your business needs

The short answer

Since February 2024, Gmail and Yahoo have asked every sender to authenticate their email with SPF or DKIM. Bulk senders must go further, with SPF, DKIM and DMARC, one-click unsubscribe and a low spam complaint rate.

Microsoft brought in similar rules for high-volume senders to Outlook.com addresses from May 2025. If your domain has SPF, DKIM and DMARC set up properly, you meet the core of all three.

Who counts as a bulk sender?

Google defines a bulk sender as one that sends close to 5,000 or more messages to personal Gmail accounts in a single day. Yahoo uses a similar idea but does not publish an exact number. Microsoft’s rules apply to domains sending more than 5,000 messages a day to its consumer addresses, such as outlook.com, hotmail.com and live.com.

The count is usually for your whole domain, not each mailbox. A business that sends a monthly newsletter to a large list can cross the line on that one day. Once Google treats you as a bulk sender, it keeps treating you as one.

Most firms send far fewer messages than this. The rules for all senders still apply to them, and receiving services trust authenticated mail more whatever the volume.

What each provider asks for

Providers update these pages from time to time. Check Google’s email sender guidelines, Yahoo’s sender best practices and Microsoft’s announcements for the current wording.

What the terms mean in plain words

• SPF is a DNS record listing the services allowed to send email for your domain.
• DKIM adds a digital signature to each message, so receivers can check it really came from you.
• DMARC tells receivers what to do when a message fails those checks. Our guide on what DMARC is and how to set it up explains it fully.
• Alignment means the domain in the “from” address matches the domain that passed SPF or DKIM.
• Forward and reverse DNS means the sending server’s name and IP address point to each other. Your email provider normally handles this.

What happens if you miss them

Mail that does not meet the rules is treated with more suspicion. In practice you may see three things.

• Delays. Messages are temporarily refused and retried, so they arrive late.
• Junk folder. Messages are accepted but filed as spam, so customers never see them.
• Rejection. Messages bounce back with an error that mentions authentication or sender policy.

The effect is often uneven. One customer gets your quote straight away, while another finds it in junk a day later. That makes the problem easy to miss until a sale is lost.

Google and Microsoft have both said they will reject more non-compliant mail over time. The safest approach is to treat the bulk sender rules as the standard for every domain. For the wider picture, read why business emails go to spam.

A checklist for your domain

1. Run our free email check to see whether your domain has SPF, DKIM and DMARC records.
2. Make sure you have exactly one SPF record that includes every service that sends for you.
3. Switch on DKIM in your main email service, such as Microsoft 365 or Google Workspace, and in each sending tool.
4. Publish a DMARC record, starting with p=none and an address for reports.
5. Check alignment. Each tool should send using your domain, not its own, in the DKIM signature.
6. Add one-click unsubscribe to newsletters and offers, and act on requests within two days.
7. Watch your complaint rate and remove people who never open or who ask to stop.
8. Send a test to a Gmail address, choose “Show original”, and confirm SPF, DKIM and DMARC all say PASS.

Getting help

Most domains need only a few careful DNS changes to meet these rules. Changes made in the wrong order can stop email arriving, so take care or ask for help. See fixing emails that go to spam and DMARC setup, or book a free call and we will look at your domain with you.