Email is still one of the highest-return marketing channels, but the rules have become much stricter. Inbox providers now reject non-compliant emails outright, and AI is increasingly the first “reader” of your message. The good news: a few technical steps and a focus on relevance keep you ahead.
The bulk sender rules are now enforced
Gmail and Yahoo started requiring stricter standards for bulk senders in February 2024. Anyone sending 5,000 or more messages a day to personal accounts must set up SPF, DKIM and DMARC authentication, offer one-click unsubscribe, and keep spam complaint rates below 0.3%. Enforcement started softly with temporary delays, but from November 2025 Gmail moved to hard enforcement: non-compliant messages are now permanently rejected before they reach any inbox.
Outlook joined in
Microsoft introduced equivalent requirements in May 2025 for domains sending more than 5,000 emails a day to Outlook.com, Hotmail.com and Live.com addresses. SPF and DKIM must pass, and DMARC must be set to at least p=none and aligned. Microsoft also places extra weight on IP reputation, so senders on shared IPs face additional risk.
Tip: p=none meets the minimum requirement, but moving towards a stricter DMARC policy gives your brand better protection against spoofing.
AI is reading your emails first
In January 2026, Google rolled Gemini-powered AI summaries into Gmail at a very large scale. Many subscribers now see your subject line, preview text and an AI summary before they read a word you wrote. Apple Intelligence can also summarise and rewrite messages.
What it means for you: put your key message and offer at the very top, use clear headings and real text rather than image-only emails, which AI, screen readers and spam filters struggle to read.
Open rates can’t be trusted anymore
Apple’s Mail Privacy Protection broke open-rate tracking back in 2021, and AI pre-fetching inflates opens further. Judge your campaigns by clicks, replies, conversions and revenue instead.
Show your logo in the inbox
BIMI (Brand Indicators for Message Identification) lets your logo appear next to your emails in supporting inboxes such as Gmail, Yahoo and Apple Mail, once your authentication is in place. It is a small detail that builds recognition and trust.
Your email checklist
- Set up SPF, DKIM and DMARC on your sending domain.
- Add one-click unsubscribe headers, not just a footer link.
- Keep spam complaints well under 0.3%.
- Never buy or scrape email lists; send only to people who opted in.
- Lead with your main message so AI summaries get it right.
- Measure clicks and conversions, not opens.
- Separate marketing and transactional emails where possible.
Sources
- MessageFlow: Email deliverability 2026
- Folderly: Gmail, Yahoo & Outlook sender requirements 2026
- PowerDMARC: Bulk email sender rules 2026
- Knak: 2026 email marketing trends
- SMTP2GO: Email marketing strategies for 2026
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