This article explains how you can send email from devices and business applications when all of your mailboxes are in Microsoft 365 or Office 365. For example:
You have a scanner, and you want to email scanned documents to yourself or someone else.
You have a line-of-business (LOB) application that manages appointments, and you want to email reminders to clients of their appointment time.
Option 1 (recommended): Authenticate your device or application directly with a Microsoft 365 or Office 365 mailbox, and send mail using SMTP AUTH client submission
Note
This option is not compatible with Microsoft Security Defaults or multi-factor authentication (MFA). If your environment uses Microsoft Security Defaults or MFA, we recommend using Option 2 or 3 below.
You must also verify that SMTP AUTH is enabled for the mailbox being used. For more information, see Enable or disable authenticated client SMTP submission (SMTP AUTH) in Exchange Online.
See Basic Authentication and Exchange Online for the latest announcements concerning this option..
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 Microsoft 365 or Office 365 using the SMTP AUTH client submission endpoint smtp.office365.com.
Each device or application must be able to authenticate with Microsoft 365 or Office 365. The email address of the account that's used to authenticate with Microsoft 365 or Office 365 will appear as the sender of messages from the device or application.
How to set up SMTP AUTH 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 AUTH client submission, the following settings will enable you to send email from your device or application.
TLS and other encryption options
Determine what version of TLS your device supports by checking the device guide or with the vendor. If your device or application does not support TLS 1.2 or above:
Use direct send (Option 2) or Microsoft 365 or Office 365 SMTP relay (Option 3) for sending mail instead (depending on your requirements).
Use an on-premises Exchange server (or another SMTP email server) if your device is unable to meet the previous requirements for connecting to Microsoft 365 or Office 365. In fact, you might find it easier to manage multiple devices and applications that send email messages in an on-premises Exchange server instead of connecting them all to Microsoft 365 or Office 365 directly. The Exchange server would relay messages in the same way that a device would use Microsoft 365 or Office 365 to relay messages using Option 3 below. You can find out more about configuring your own email server to send emails to Microsoft 365 or Office 365 here: Set up connectors to route mail between Microsoft 365 or Office 365 and your own email servers.
Note
If your device recommends or defaults to port 465, it does not support SMTP AUTH client submission.
How SMTP AUTH client submission works
The following diagram gives you a conceptual overview of what your environment will look like.
Features of SMTP AUTH client submission
SMTP AUTH client submission allows you to send email to people in your organization and outside your company.
This method bypasses most spam checks for email sent to people in your organization. This can help protect your company IP addresses from being blocked by a spam list.
With this method, you can send email from any location or IP address, including your (on-premises) organization's network, or a third-party cloud hosting service, like Microsoft Azure.
Requirements for SMTP AUTH client submission
Authentication: You must be able to configure a username and password to send email on the device. You cannot use Microsoft Security Defaults or multi-factor authentication (MFA), which disable basic authentication and are designed to protect your users from compromise. If your environment uses Microsoft Security Defaults or MFA, we recommend using Option 2 or 3 below.
Mailbox: You must have a licensed Microsoft 365 or Office 365 mailbox to send email from.
Transport Layer Security (TLS): Your device must be able to use TLS version 1.2 and above.
Port: Port 587 (recommended) or port 25 is required and must be unblocked on your network. Some network firewalls or ISPs block ports, especially port 25.
DNS: You must use the DNS name smtp.office365.com. Do not use an IP address for the Microsoft 365 or Office 365 server, as IP Addresses are not supported.
Note
For information about TLS, see How Exchange Online uses TLS to secure email connections and for detailed technical information about how Exchange Online uses TLS with cipher suite ordering, see Enhancing mail flow security for Exchange Online.
Limitations of SMTP AUTH client submission
You can only send from one email address unless your device can store login credentials for multiple Microsoft 365 or Office 365 mailboxes. Microsoft 365 or Office 365 imposes a limit of 30 messages sent per minute, and a limit of 10,000 recipients per day.
Option 2: Send mail directly from your printer or application to Microsoft 365 or Office 365 (direct send)
Choose this option when:
Your environment uses Microsoft Security Defaults or multi-factor authentication (MFA).
SMTP client submission (Option 1) is not compatible with your business needs or with your device.
You only need to send messages to recipients in your own organization who have mailboxes in Microsoft 365 or 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. Microsoft 365 or 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 Microsoft 365 or 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:
Step-by-step instructions for direct send
If your device or application can send from a static public IP address, obtain this IP address and make a note of it. You can share your static IP address with other devices and users, but don't share the IP address with anyone outside of your company. Your device or application can send from a dynamic or shared IP address but messages are more prone to antispam filtering.
Sign in to the Microsoft 365 admin center.
Go to Settings > Domains, select your domain (for example, contoso.com), and find the MX record.
The MX record will have a Points to address or value value that looks similar to
contoso-com.mail.protection.outlook.com.Make a note of the MX record Points to address or value value, which we refer to as your MX endpoint.
Go back to the device, and in the settings, under what would normally be called Server or Smart Host, enter the MX record POINTS TO ADDRESS value you recorded in step 4.
Note
Do NOT use an IP address for the Microsoft 365 or Office 365 server connection, as IP addresses are not supported.
Now that you are done configuring your device settings, go to your domain registrar's website to update your DNS records. Edit your sender policy framework (SPF) record. In the entry, include the IP address that you noted in step 1. The finished string looks similar to this:
v=spf1 ip4:10.5.3.2 include:spf.protection.outlook.com ~allwhere 10.5.3.2 is your public IP address.
Note
Skipping this step might cause email to be sent to recipients' junk mail folders.
To test the configuration, send a test email from your device or application, and confirm that the recipient received it.
How direct send works
In the following diagram, the application or device in your organization's network uses direct send and your Microsoft 365 or Office 365 mail exchange (MX) endpoint to email recipients in your organization. It's easy to find your MX endpoint in Microsoft 365 or Office 365 if you need to look it up.
You can configure your device to send email direct to Microsoft 365 or Office 365. Use direct send to relay email to recipients with Microsoft 365 or Office 365 mailboxes in your organization. Direct send also works for external recipients with mailboxes in Microsoft 365 or Office 365. If your device uses direct send to try to relay an email for a recipient who doesn't have a Microsoft 365 or Office 365 mailbox, the email will be rejected.
Note
If your device or application has the ability to act as a email server to deliver messages to Microsoft 365 or Microsoft 365 or Office 365 as well as other email providers, there are no Microsoft 365 or Office 365 settings needed for this scenario. Consult your device or application instructions for more information.
Features of direct send
Uses Microsoft 365 or Office 365 to send emails, but does not require a dedicated Microsoft 365 or Office 365 mailbox.
Doesn't require your device or application to have a static IP address. However, this is recommended if possible.
Doesn't work with a connector; never configure a device to use a connector with direct send, this can cause problems.
Doesn't require your device to support TLS.
Direct send has higher sending limits than SMTP client submission. Senders are not bound by the 30 messages per minute or 10,000 recipients per day limit.
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. This 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.
Option 3: Configure a connector to send mail using Microsoft 365 or Office 365 SMTP relay
This option is more difficult to implement than the others. Only choose this option when:
Your environment uses Microsoft Security Defaults or multi-factor authentication (MFA).
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 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 a more complicated option.
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:
Step-by-step configuration instructions for SMTP relay
Obtain the public (static) IP address that the device or application with send from. A dynamic IP address isn't supported or allowed. You can share your static IP address with other devices and users, but don't share the IP address with anyone outside of your company. Make a note of this IP address for later.
Sign in to the Microsoft 365 admin center.
Go to Settings > Domains, select your domain (for example, contoso.com), and find the MX record.
The MX record will have a Points to address or value value that looks similar to
contoso-com.mail.protection.outlook.com.Make a note of the MX record Points to address or value value, which we refer to as your MX endpoint.
Check that the domains that the application or device will send to have been verified. If the domain is not verified, emails could be lost, and you won't be able to track them with the Exchange Online message trace tool.
In Microsoft 365 or Office 365, select Admin and then Exchange to go to the Exchange admin center.
In the Exchange admin center, go to Mail flow > Connectors.
Check the list of connectors set up for your organization. If there is no connector listed from your organization's email server to Microsoft 365 or Office 365, create one:
a. To start the wizard, click the plus symbol +.
b. On the first screen, choose the options that are depicted in the following screenshot:
c. Click Next, and give the connector a name.
d. On the next screen, choose the option By verifying that the IP address of the sending server matches one of these IP addresses that belong to your organization, and add the IP address from step 1.
e. Leave all the other fields with their default values, and select Save.
Now that you are done with configuring your Microsoft 365 or Office 365 settings, go to your domain registrar's website to update your DNS records. Edit your SPF record. Include the IP address that you noted in step 1. The finished string should look similar to this
v=spf1 ip4:10.5.3.2 include:spf.protection.outlook.com ~all, where 10.5.3.2 is your public IP address. Skipping this step can cause email to be sent to recipients' junk mail folders.Now, go back to the device, and in the settings, find the entry for Server or Smart Host, and enter the MX record POINTS TO ADDRESS value that you recorded in step 3.
To test the configuration, send a test email from your device or application, and confirm that it was received by the recipient.
Configure a certificate-based connector to relay email through Microsoft 365 or Office 365
If your devices or applications are capable of using a certificate for mail flow, you can configure a certificate-based connector to relay email through Microsoft 365 or Office 365.
To do this, verify the subject name on the certificate used by the sending device or application. The common name (CN) or subject alternative name (SAN) in the certificate should contain a domain name that you have registered in Microsoft 365 or Office 365. Also, you must create a certificate-based connector in Microsoft 365 or Office 365 with this same domain name to accept and relay emails coming from these devices, applications, or any other on-premises server. For more information about this method, see important notice for email customers who have configured connectors.
How Microsoft 365 or Office 365 SMTP relay works
In the following diagram, the application or device in your organization's network uses a connector for SMTP relay to email recipients in your organization.
The Microsoft 365 or Office 365 connector that you configure authenticates your device or application with Microsoft 365 or Office 365 using an IP address. Your device or application can send email using any address (including ones that can't receive mail), as long as the address uses one of your domains. The email address doesn't need to be associated with an actual mailbox. For example, if your domain is contoso.com, you could send from an address like do_not_reply@contoso.com.
Microsoft 365 or Office 365 SMTP relay uses a connector to authenticate the mail sent from your device or application. This allows Microsoft 365 or Office 365 to relay those messages to your own mailboxes and external recipients. Microsoft 365 or Office 365 SMTP relay is similar to direct send except that it can send mail to external recipients.
Due to the added complexity of configuring a connector, direct send is recommended over Microsoft 365 or Office 365 SMTP relay, unless you must send email to external recipients. To send email using Microsoft 365 or Office 365 SMTP relay, your device or application server must have a static IP address or address range. You can't use SMTP relay to send email directly to Microsoft 365 or Office 365 from a third-party hosted service, such as Microsoft Azure. For more information, see Troubleshoot outbound SMTP connectivity issues in Azure.
Features of Microsoft 365 or Office 365 SMTP relay
Microsoft 365 or Office 365 SMTP relay does not require the use of a licensed Microsoft 365 or Office 365 mailbox to send emails.
Microsoft 365 or Office 365 SMTP relay has higher sending limits than SMTP client submission; senders are not bound by the 30 messages per minute or 10,000 recipients per day limits.
Requirements for Microsoft 365 or Office 365 SMTP relay
Static IP address or address range: Most devices or applications are unable to use a certificate for authentication. To authenticate your device or application, use one or more static IP addresses that are not shared with another organization.
Connector: You must set up a connector in Exchange Online for email sent from your device or application.
Port: Port 25 is required and must not be blocked on your network or by your ISP.
Licensing: SMTP relay doesn't use a specific Microsoft 365 or Office 365 mailbox to send email. This means that users must have their own licenses if they send email from devices or applications that are configured for SMTP relay. If you have senders who use a device or LOB application and those senders do not have Microsoft 365 or Office 365 mailbox licenses, obtain and assign an Exchange Online Protection license to each unlicensed sender. This is the least expensive license that allows you to send email via Microsoft 365 or Office 365.
Limitations of Microsoft 365 or Office 365 SMTP relay
Sent mail can be disrupted if your IP addresses are blocked by a spam list.
Reasonable limits are imposed for sending. For more information, see High-risk delivery pool for outbound messages.
Requires static unshared IP addresses (unless a certificate is used).
Compare the options
Here's a comparison of each configuration option and the features they support.
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