For years deliverability was something you only looked at when the numbers disappointed. Since February 2024 it is an entry requirement. Google and Yahoo set hard conditions for anyone sending more than 5,000 messages a day to their users. Microsoft drew the same line on 5 May 2025 for Outlook.com, Hotmail.com and Live.com.
What is actually required
- SPF and DKIM on the sending domain, both valid, and resolving to the same domain as the visible sender
- A DMARC record with at least p=none, aligned with SPF or DKIM, and preferably with both
- A one-click unsubscribe in the header of every commercial message, with unsubscribes processed within two days
- A spam complaint rate below 0.30 percent, with 0.10 percent as the number you want to stay under
The technique is the easy part
SPF, DKIM and DMARC are a one-off job in DNS. An afternoon, a day at most when several sending parties share one domain. Where it goes wrong is alignment: a mail tool that signs perfectly well, but on its own domain, still fails DMARC. You only see that when you read the DMARC reports, so somebody has to read them.
The complaint rate is the real work
You do not reach 0.10 percent with technique but with discipline. One in a thousand recipients may mark your newsletter as spam. That only works when the people on your list signed up deliberately, when they know what for, and when unsubscribing is easier than the spam button. A bought list, a signup from three years ago, or an unsubscribe link that first asks for a password: those are the three causes I run into most.
What I work through before the first send
- Check SPF, DKIM and DMARC and test alignment with a real test send to Gmail, Yahoo and Outlook
- Check the one-click unsubscribe in the header, not just the link in the footer
- Switch on Google Postmaster Tools, so you can see the complaint rate instead of guessing it
- Clean the list: hard bounces out, addresses without interaction in the last twelve months set apart
- Send a reactivation campaign to those dormant addresses, and politely unsubscribe whoever does not respond
Unsubscribing people feels wrong when you are judged on list growth. But a list of 8,000 people who open and click delivers more than 20,000 addresses dragging your reputation down, and by now it is simply the condition for getting in at all.