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Authentication, one-click unsubscribe and low complaint rates are no longer optional. Here is a step-by-step playbook for marketers.
Email remains one of the highest-return marketing channels — but only if messages reach the inbox. Since February 2024, when Google and Yahoo introduced new requirements for bulk senders, deliverability has become a technical discipline. Microsoft followed with similar requirements for high-volume senders to Outlook consumer addresses in 2025, and enforcement across providers has tightened since.
If your open rates are falling or your emails are landing in spam, this guide explains why and what to fix.
Google defines bulk senders as those sending close to 5,000 or more messages a day to Gmail accounts. Once a domain qualifies, it is generally treated as a bulk sender going forward. However, the best practices below help every sender.
| Protocol | What it does |
|---|---|
| SPF (Sender Policy Framework) | Lists which servers can send email for your domain |
| DKIM (DomainKeys Identified Mail) | Adds a cryptographic signature proving the message was not altered |
| DMARC (Domain-based Message Authentication, Reporting and Conformance) | Tells receivers what to do if SPF/DKIM fail and sends you reports |
Bulk senders must set up SPF, DKIM and DMARC. A DMARC policy of at least p=none is required, and the visible From domain should align with SPF or DKIM.
Example DMARC record:
v=DMARC1; p=none; rua=mailto:dmarc-reports@example.comOnce you are confident legitimate mail passes, move gradually toward p=quarantine or p=reject to protect your brand from spoofing.
Marketing emails must support one-click unsubscribe through the List-Unsubscribe and List-Unsubscribe-Post headers, with a visible unsubscribe link in the message. Unsubscribe requests should be honoured within two days.
Google asks senders to keep the spam rate reported in Postmaster Tools below 0.3%, and ideally below 0.1%. Crossing the threshold can quickly damage inbox placement.
Sending domains and IPs should have valid forward and reverse DNS records, and connections should use TLS encryption.
Start with small volumes sent to your most engaged subscribers, then increase gradually over several weeks. Sudden large sends from new infrastructure look like spam behaviour.
Many Indian brands send large volumes of transactional and promotional email alongside SMS and WhatsApp. Poor deliverability can quietly reduce revenue from every campaign. Getting authentication right also protects customers from phishing emails that spoof your brand.
The strictest rules target bulk senders, but all senders are expected to authenticate and follow best practice. Following them improves deliverability for everyone.
Below 0.1% is a healthy target; staying under 0.3% is required for bulk senders to Gmail.
It enables monitoring but does not block spoofed mail. Stronger policies (quarantine or reject) provide protection.
The one-click requirement focuses on marketing and subscribed messages, but all emails still need authentication.
Inbox placement is now earned through technical trust and genuine engagement. Authenticate properly, make unsubscribing easy, clean your lists and monitor your reputation — and email can remain one of your most profitable channels.