How to configure SMTP Relay on Office 365

Introduction

Sending emails can be tricky. From poor deliverability to IP blacklisting, you can run into a lot of issues. However, an SMTP relay service can solve a lot of these issues. SMTP relay is a mail server or MTA (Mail Transfer Agent) that is directed to hand off your message to another mail server that can get your message closer to its intended recipient. In this tutorial, you will learn how to configure SMTP relay on Office 365 to allow it to send mails in and out of your organization.

Requirements

• An active Microsoft 365 / Office 365 subscription with a mailbox whose login details you know.
• An application, server or device that can send email via SMTP (for example a web application running on a VPS or Dedicated Server from Snel.com).
• A configured SMTP Relay (Smarthost) or the intention to configure one.
• The application must support SMTP authentication and TLS 1.2 or higher.
• Access to the SMTP settings of the application or device so you can enter
  the server name, port, username and password.

Now, since the port 25 is blocked over at Snel, you can use the direct method of sending mail via Office 365.

How to set up SMTP relay Authentication

You need to enter the following values in your application settings for SMTP. The settings or terminology can differ depending on the application you are using though.

Server/Smart Host: smtp.office365.com
Port: 587
TLS/Start TLS: Enabled
Username/Email address and password: Enter the sign-in credentials of the mailbox over at your Office 365 Account

Conclusion

This concludes our tutorial for configuring SMTP relay on Office 365. You should now be able to send mails using your applications or devices properly.