Outlook Announces New Sender Requirements

Outlook Announces New Sender Requirements

A year after Google and Yahoo! started enforcing their new list of sender requirements, Outlook announced that they will have their own set of sender requirements. This set of rules will apply to the Outlook.com consumer service, which includes Outlook.com, Hotmail.com, and Live.com.  

Who Will Be Impacted? 

As stated in their news release, this will impact domains that are sending more than 5,000 emails per day. “In an era where email remains one of the most widely used tools for personal and business communications, Outlook is stepping up its commitment to protect inboxes and preserve trust in the digital ecosystem. Today, we’re announcing new requirements and best practices designed to strengthen email authentication for domains sending more than 5,000 emails per day” - Puneeth (Microsoft). 

Requirements

Outlook will begin to require SPF, DKIM, and DMARC compliance. If messages are deemed to be non-compliant, they will first be delivered to the junk folder and in the future, they might be rejected altogether. 

1. SPF (Sender Policy Framework)

   •  IP(s) being used to send mail must be allowed to send mail for that sending domain.

2. DKIM (DomainKeys Identified Mail)

   • Must pass for the domain being used to send mail.

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

   • Only a policy of ‘none’ is required and there must be alignment with SPF or DKIM (ideally both). 

Recommendations

Outside of the DNS requirements, Outlook also included four email hygiene recommendations that senders should follow in order to maintain ‘quality and trust’:

1. Compliant Sender Address

   • The “From” or “Reply‐To” address needs to not only be valid, but also reflect the true sending domain. Microsoft also states that this email address should be able to receive replies. 

2. Functional Unsubscribe Links

   • For marketing and bulk mail, make sure the recipient can easily find the unsubscribe link and go through the unsubscribe process. 

3. Bounce Management

   • Be sure to remove all invalid emails from your database on a regular basis. In the FAQs included in their news release, Outlook states that senders should remove inactive or invalid email addresses regularly (monthly or quarterly). 

4. Transparent Mailing Practices

   • Outside of making sure you are only sending to recipients that have consented to receive your emails, make sure that you use accurate subject lines and avoid deceptive headers. 

If Outlook detects that a sender is not following any of the hygiene recommendations above, they could filter messages to the spam folder or outright block the emails. 

Timeline

Beginning May 5, 2025, Outlook will begin to enforce the new set of sender rules and will begin delivering messages from domains sending at least 5,000 emails a day that are not compliant to the junk folder. At some point, that will change and Outlook could start to outright block mail from non-compliant domains, although they have not yet released that date yet. 

What Should Senders Do?

Similar to when Gmail and Yahoo! released their list of sender rules, step one is to ensure compliance. Well before May 5th, if you are sending more than 5,000 emails per day,  you need to make sure that your emails are passing SPF, DKIM, and DMARC. It’s also important to look through the hygiene recommendations to make sure you are following those best practices. Our Expert Services helped many senders prepare for the new sender rules laid out by Google and Yahoo! and are ready to help you prepare for Outlook’s sender rules.