There are three options available with Microsoft 365 for sending email from your devices, applications and endpoints.
The following settings will enable you to send emails from your email client, device or application.
| Device or Application setting | Value |
| Server/smart host | smtp.office365.com |
| Port | Port 587 (recommended) or port 25 |
| TLS/StartTLS | Enabled |
| Username/email address and password | Enter the sign-in credentials of the hosted mailbox being used |
The second option is to send mail directly from your device or application to Microsoft 365
Settings for direct send, Enter the following settings on the device or in the application directly.
| Device or application setting | Value |
| Server/smart host |
Your MX endpoint, for example, |
| Port | Port 25 |
| TLS/StartTLS | Optional |
| Email address | Any email address for one of your Microsoft 365 or Office 365 accepted domains. This email address does not need to have a mailbox. |
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:
| DNS entry | Value |
| SPF | v=spf1 ip4:<Static IP Address> include:spf.protection.outlook.com ~all |
Requirements for direct send
- Port: Port 25 is required and must be unblocked on your network.
- Static IP address is recommended: A static IP address is recommended so that an SPF record can be created for your domain. The SPF record helps avoid your messages being flagged as spam.
- Does not require a Microsoft 365 or Office 365 mailbox with a license.
Limitations of direct send
- Direct send cannot be used to deliver email to external recipients, for example, recipients with Yahoo or Gmail addresses.
- Your messages will be subject to antispam checks.
- Sent mail might be disrupted if your IP addresses are blocked by a spam list.
- Microsoft 365 and Office 365 use throttling policies to protect the performance of the service.
The third option is by configuring a connector to send mail using Microsoft 365
SMTP relay lets Microsoft 365 or Office 365 relay emails on your behalf by using a connector that's configured with your public IP address or a TLS certificate. Setting up a connector makes this option more complicated.
Settings for Microsoft 365 or Office 365 SMTP relay
| Device or application setting | Value |
| Server/smart host | Your MX endpoint, for example, yourdomain-com.mail.pr-otection.outlook.com |
| Port | Port 25 |
| TLS/StartTLS | Enabled |
| Email address | Any email address in one of your Microsoft 365 or Office 365 verified domains. This email address does not need a mailbox. |
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:
| Connector setting | Value |
| From | Your organization's email server |
| To | Microsoft 365 or Office 365 |
| Domain restrictions | IP address/range Your on-premises IP address or address range that the device or application will use to connect to Microsoft 365 or Office 365 |
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:
| DNS entry | Value |
| SPF | v=spf1 ip4:<Static IP Address> include:spf.protection.outlook.com ~all |
For detailed information on setting up various SMTP options with Microsoft 365 Read this important article at Microsoft.
