Rules for every sender
Authenticate mail with SPF or DKIM, have valid forward and reverse DNS for sending servers, use TLS, and keep the spam complaint rate reported in Google Postmaster Tools below 0.3% (ideally under 0.1%).
Guide
Bulk sender requirements for Gmail, Yahoo, and Outlook
The authentication, unsubscribe, and spam-rate rules the biggest mailbox providers enforce — and a checklist to meet them.
In short
Since February 2024, Google and Yahoo require anyone sending about 5,000 or more messages a day to their users to authenticate with SPF and DKIM, publish a DMARC policy, align the From domain, support one-click unsubscribe (RFC 8058) and honor it within two days, and keep spam complaint rates below 0.3%. Microsoft applied similar SPF, DKIM, and DMARC rules to Outlook.com in 2025.
Extra rules for bulk senders
Senders of roughly 5,000+ messages a day to Gmail or Yahoo users must use both SPF and DKIM, publish DMARC (p=none is acceptable), align the From domain with SPF or DKIM, include a List-Unsubscribe header with one-click (RFC 8058) support for marketing mail, and process unsubscribes within two days.
Microsoft Outlook.com
From May 2025, Microsoft requires high-volume senders to Outlook.com, Hotmail, and Live addresses to pass SPF, DKIM, and DMARC (at least p=none, aligned with SPF or DKIM). Non-compliant mail may be junked or rejected.
How Infiara helps
Infiara adds a List-Unsubscribe header with List-Unsubscribe-Post one-click support to every campaign email, suppresses unsubscribed addresses permanently, can pause a mailbox on a bounce spike, and shows SPF, DKIM, and DMARC status for your domain.
Questions
Frequently asked questions
Do these rules apply to one-to-one cold email?
The authentication and spam-rate rules apply to everyone. The 5,000-per-day threshold triggers the stricter bulk rules, and once a domain is classed as a bulk sender it stays classed that way, so it is safest to meet all of them.
Where do I check my spam rate?
Google Postmaster Tools reports spam rate and domain reputation for mail sent to Gmail users once you verify your domain.
More from Infiara
Keep reading
- Cold email softwareAI cold email software for Gmail, Google Workspace, Microsoft 365, and SMTP. Personalize every send, follow up until they reply, and turn replies into tasks.
- What is cold email?Cold email is a personalized one-to-one email to someone you don’t know yet. How it differs from spam, the rules that apply, and a good example.
- Gmail & Outlook sending limitsHow many emails can you send per day from Gmail, Google Workspace, and Microsoft 365? Published daily limits and how to stay safely under them.
- SPF, DKIM & DMARC setupSet up SPF, DKIM, and DMARC for Google Workspace or Microsoft 365 so your emails are authenticated and reach the inbox. Includes example DNS records.
- Follow-up email templatesShort follow-up email templates for when a prospect has not replied: the bump, the value add, and the polite close. Plus timing tips and when to stop.
- Cold email lawsWhat CAN-SPAM, GDPR, and CASL mean for B2B cold email: sender identity, opt-out, lawful basis, and consent. A plain-English overview, not legal advice.
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