Microsoft joins Google and Yahoo with stronger sender requirements
As of May 2025, Microsoft has joined Google and Yahoo in implementing stronger sender requirements. The good news is that if you’re technically compliant with Google and Yahoo, then you’re also automatically compliant with Microsoft’s technical requirements. Dotdigital customers do not need to make any technical changes; sending domains are automatically set up to meet authentication requirements for all major mailbox providers.
Wait – Google and Yahoo implemented stronger sender requirements?
I envy your blissful ignorance. Let me recap our blog post for your convenience. As of February 2024, Gmail and Yahoo required brands sending more than 5k emails per day to their users to comply with 3 requirements:
- Implement authentication: SPF, DKIM, and DMARC
- Make unsubscribing easy: include both a list-unsubscribe technical header supporting one-click unsubscribe and an unsubscribe link in the body of all promotional emails
- Send wanted mail: keep spam complaint rates below 0.3%
Failure to meet these criteria can result in delays in emails being delivered, emails landing in the spam folder, or even emails not being delivered at all, i.e., bouncing.
For Dotdigital customers, we take care of the authentication and list-unsubscribe technical headers for you. Just make sure you’re including an easy-to-find unsubscribe link in the body of your marketing emails and keep an eye on your spam complaint rates using your account reporting and Google Postmaster Tools.
What has Microsoft changed?
Like Google and Yahoo, Microsoft has announced that it requires technical authentication for any domain sending more than 5k emails per day to Outlook recipients. Outlook covers outlook.com, hotmail.com, and live.com domains as well as their regional variations such as hotmail.co.uk.
The authentication requirements are:
- SPF must pass for the sending domain
- DKIM must pass
- DMARC with at least a p=none policy is required
Microsoft has also clarified its recommended hygiene practices for high volume senders:
- Use a valid from address that can accept replies
- Make unsubscribe easy
- Regularly suppress invalid addresses
- Send to recipients who have provided consent
- Avoid deceptive practices such as misleading subject lines
Clearer guidance for marketers
Deliverability experts have long been evangelizing best practices for achieving inbox placement, and it’s great to see Microsoft echo what we’ve also heard from Gmail and Yahoo. Advice to marketers for strong deliverability has never been more clear, and it’s coming straight from the horse’s mouth:
- Consent: Opt-in is mandatory, and double or confirmed opt-in is recommended as best practice
- Unsubscribe: Make unsubscribing easy and honor unsubscribes quickly
- List hygiene: Regularly remove invalid and inactive contacts from your database
- Purchased data: Buying lists of contacts is prohibited and bad for your reputation and deliverability
- Content: Should be transparent; don’t use misleading headers or subject lines
- Frequency: Honor the expectations set at time of opt-in, and provide ways for your subscribers to change or reduce frequency of mailings
Marketers and mailbox providers unite
Now that Microsoft has aligned its sender requirements with those of Google and Yahoo, the industry is truly speaking with one voice: authentication, consent, transparency, and hygiene are required for successful inbox placement.
Dotdigital customers continue to be ahead of the curve. We handle the technical stuff for you (like domain authentication and list-unsubscribe headers) so you can focus your marketing expertise on sending relevant, wanted emails to engaged contacts.
If you have questions about your deliverability performance or want help in creating a strategy optimized for the inbox, our Dotdigital Deliverability Consultants are here to help. Reach out to your CSM to ask about our deliverability products.
