How to enable on-premises applications and devices to send mail to Office 365 users

This article describes how to enable on-premises line-of-business (LOB) applications and devices to send mail to Microsoft Office 365 mailboxes. You may want to do this in situations in which you migrated all your mailboxes to Office 365 but where you don't have an on-premises mail server such as Microsoft Exchange Server. For example, you may want to send mail from on-premises printers or scanners to Office 365 users.

Note This article describes how to enable on-premises LOB applications and devices to send mail to Office 365 mailboxes only in a domain for which you are authoritative. This article doesn't discuss how to enable applications to use Office 365 transport servers to relay to other domains that you own. The mail relay scenario is beyond the scope of this article. For more information about how to set up a mail relay in Office 365, see the following Microsoft Knowledge Base article:

To enable on-premises LOB applications and devices to send mail to Office 365 mailboxes, you must install and configure Internet Information Services (IIS). To do this, follow these steps:

1. Install IIS on an internal server. During installation, select the option to install the Simple Mail Transfer Protocol
   (SMTP) components.
2. In IIS Manager, expand Default SMTP Virtual Server, and then click Domains.
3. Right-click Domains, click New, click Domain, and then click Remote.
4. In the Name box, type the name of your domain. For example, type contoso.com. Then, click Finish.
5. Double-click the domain that you just created.
6. Click to select the Allow incoming mail to be relayed to this domain check box.
7. In the Route domain area, click Use DNS to route to this domain.
8. Click Outbound Security, click to select the TLS encryption check box, and then click OK.
9. Right-click Default SMTP Virtual Server, and then click Properties.
10. On the Delivery tab, click Outbound Connections.
11. In the TCP Port box, type 25, and then click OK.
12. Click Outbound Security, click to select the TLS encryption check box, and then click OK.
13. On the Access tab, click Authentication, click to select the Anonymous access check box, and then click OK.
14. On the Relay tab, select Only the list below, type the IP addresses of the client computers (LOB applications ) that will be sending email messages, and then click OK.
15. Test to confirm that you can send mail from the LOB application.

Still need help? Go to the Office 365 Community website.