Using Office 365 for SMTP Relay

Here I can show you how you would setup a device or an application to send email via office 365 as an SMTP relay.

As an example: You have a scanner, and you want to email scanned documents to yourself or someone else. or you have a line-of-business (LOB) application that handles invoicing, like QuickBooks, and you want to configure it to use an Billing account setup as an Office 365 mailbox.

Option 1: Authenticate your device or application directly with an Office 365 mailbox, and send mail using SMTP client submission

This option supports most usage scenarios and it’s the easiest to set up. Choose this option when:

• You want to send email from a third-party hosted application, service, or device.
• You want to send email to people inside and outside your organization.

To configure your device or application, connect directly to Office 365 using the SMTP client submission endpoint smtp.office365.com.

Each device/application must be able to authenticate with Office 365. It can have its own sender address, or all devices can use one address, such as printer@contoso.com.

How to set up SMTP client submission

Enter the following settings directly on your device or in the application as their guide instructs (it might use different terminology than this article). As long as your scenario meets the requirements for SMTP client submission, the following settings will enable you to send email from your device or application.

Option 2: Send mail directly from your printer or application to Office 365 (direct send)

Choose this option when:

• SMTP client submission (Option 1) is not compatible with your business needs or with your device. For example, your device or application does not meet the requirements of SMTP client submission, such as TLS support.
• You only need to send messages to recipients in your own organization who have with mailboxes in Office 365; you don’t need to send email to people outside of your organization.

Other scenarios when direct send may be your best choice:

• You want your device or application to send from each user’s email address and do not want each user’s mailbox credentials configured to use SMTP client submission. Direct send allows each user in your organization to send email using their own address. Avoid using a single mailbox with Send As permissions for all your users. This method is not supported because of complexity and potential issues.
• You want to send bulk email or newsletters. Office 365 does not allow you to do this via SMTP client submission. Direct send allows you to send a high volume of messages. Note that there is a risk of your email being marked as spam by Office 365. You might want to enlist the help of a bulk email provider to assist you. For example, they’ll help you adhere to best practices, and can help ensure that your domains and IP addresses are not blocked by others on the Internet.

Settings for direct send

Enter the following settings on the device or in the application directly.

We recommend adding an SPF record to avoid having messages flagged as spam. If you are sending from a static IP address, add it to your SPF record in your domain registrar’s DNS settings as follows:

Option 3: Configure a connector to send mail using Office 365 SMTP relay

This option is more difficult to implement than the others. Only choose this option when:

• SMTP client submission (Option 1) is not compatible with your business needs or with your device
• You can’t use direct send (Option 2) because you must send email to external recipients.

SMTP relay lets Office 365 relay emails on your behalf by using your public IP address (or a certificate) to authenticate Office 365. To do this, you’ll need to set up a connector for your Office 365 account, which is what makes this a more complicated configuration.

Settings for Microsoft 365 or Office 365 SMTP relay

If you already have a connector that’s configured to deliver messages from your on-premises organization to Microsoft 365 or Office 365 (for example, a hybrid environment), you probably don’t need to create a dedicated connector for Microsoft 365 or Office 365 SMTP relay. If you need to create a connector, use the following settings to support this scenario:

We recommend adding an SPF record to avoid having messages flagged as spam. If you are sending from a static IP address, add it to your SPF record in your domain registrar’s DNS settings as follows:

Compare the options

Here’s a comparison of each configuration option and the features they support.