Authenticate every message
Providers expect SPF and DKIM on all mail, and a DMARC policy for bulk senders. Google and Yahoo introduced this as a requirement for bulk senders in 2024, and Microsoft has set similar expectations for high-volume senders to its consumer mailboxes.
Your From domain should align with the domain that SPF or DKIM validates. See the DKIM, SPF and DMARC guide for the setup.
Keep complaints low
Providers track the share of recipients who mark your mail as spam. Google has said bulk senders should stay under 0.10% in Postmaster Tools and never reach 0.30%, and Yahoo publishes similar guidance.
Complaint rates are calculated by each provider, so use their own tools, such as Google Postmaster Tools, to watch yours. A short spike matters less than a steady rate.
Make unsubscribing easy
Bulk and marketing mail should include one-click unsubscribe headers, and you should honour requests promptly. Google and Yahoo ask for removal within two days for marketing mail.
Add both headers so that providers can show their own unsubscribe button. Also include a visible unsubscribe link in the message.
List-Unsubscribe: <mailto:unsub@example.com>, <https://example.com/unsubscribe?id=ID> List-Unsubscribe-Post: List-Unsubscribe=One-Click
Send mail people want
Engagement is a signal. Remove recipients who never open or click, collect addresses with clear consent, and avoid purchased or scraped lists, which bring spam traps and complaints.
Send at a steady pace, keep your content honest, and make the sender name and subject match what the recipient expects.
Operate responsibly
Use valid forward and reverse DNS for sending IPs, keep a consistent From identity, use TLS, and keep bounce rates low by removing addresses that hard-bounce.
If you share an IP with other senders, their behaviour affects you. A dedicated IP gives you control but needs warmup and steady volume.
Check the source
Thresholds, volume definitions and dates change. Before you rely on any number here, read the current sender guidelines published by Google, Yahoo and Microsoft, and treat this page as a map to what they cover rather than a replacement for them.
If you want a second pair of eyes, our deliverability audit reviews your authentication, complaint signals and list practices against the current requirements.