Outlooks New Requirements for High Volume Senders

Microsoft is stepping up its game to create a safer, more trustworthy email environment. Beginning May 5, 2025, any domain sending more than 5,000 emails per day to Outlook.com addresses must comply with stricter email authentication standards, or risk landing in the Junk folder.

If you're a business or marketer relying on email as a critical channel, this change is a game-changer

What’s Changing

To enhance deliverability and reduce spam, Microsoft is mandating the implementation of three key email authentication protocols:

1. SPF (Sender Policy Framework)

Your DNS records must list all IP addresses that are authorised to send emails on your behalf. Without this, Outlook will treat your messages as suspect.

2. DKIM (DomainKeys Identified Mail)

This ensures that your messages haven’t been tampered with and confirms the identity of the sender. It adds a digital signature to your emails, which Outlook will now require.

3. DMARC (Domain-based Message Authentication, Reporting & Conformance)

This policy tells Outlook what to do when SPF and/or DKIM checks fail. At a minimum, you need to have a DMARC record with a p=none policy, but aligning with both SPF and DKIM is ideal.

Failure to comply means your emails could go straight to Junk, damaging your reputation and reducing engagement

Best Practices Moving Forwar

Microsoft’s requirements align with what responsible senders should already be doing. Now’s the time to make sure your practices are up to par:

• Use Valid From/Reply-To Addresses: Make sure recipients can respond to a real, monitored address.
• Ensure One-Click Unsubscribes: Marketing messages must include a visible and functional unsubscribe link.
• Maintain a Clean List: Regularly remove invalid addresses and inactive contacts.
• Be Transparent: No misleading headers or subject lines. Always get consent before sending.