This site provides information to information technology professionals who administer systems that send email to and receive email from Outlook.com. It also provides some information about how users with Outlook.com accounts can report junk email and phishing attempts. However, it is not intended to provide extensive support to Outlook.com users. If you are an Outlook.com user in need of support, please visit Microsoft Support.

To navigate this site please use the navigation links to the left, or to jump right to the most requested information please click on one of the links below.

• I am an Outlook.com user in need of support.
• Email I send is being blocked or junked by Outlook.com.
• I want information about SMTP error codes returned by Outlook.com servers.

Announcements

We are aware of an issue that may result in certain IP addresses being temporarily rejected at higher rates. We are actively investigating the issue. Please continue to submit tickets if you are experiencing this problem.

Requirements for High-Volume Senders

Starting May 5th, 2025, Outlook.com is enforcing stricter email authentication standards (SPF, DKIM, DMARC) for domains sending over 5,000 emails per day to enhance security and reduce spam. Non-compliant messages will be sent to messages will be sent to the junk folder. Shortly we will reject the messages until the DNS records are corrected.

Learn more about these changes and how to prepare in our recent blog post:
Strengthening Email Ecosystem: Outlook’s Requirements for High‐Volume Senders.

Postmaster Site

Welcome to the Outlook.com Postmaster site. We've created this site in order to help senders improve their reputations and increase deliverability into Outlook.com inboxes.