Your company decided to use Exchange Online for e-mail, but leave the SharePoint Servers on-prem. After doing this you may have noticed that Exchange Online will not be able to deliver e-mail to the Drop folder, were SharePoint processes email for delivery. At this point the incoming e-mail feature in SharePoint is totally non-functional.
There is no need to panic, there is simple solution!
Since Exchange Online is “Online”, it will need access to an On-Prem SMTP Server to deliver e-mail to a DROP folder. This is where SharePoint process email for delivery to list and libraries. Most of this is or was in place before moving to Exchange Online, but opening ports on the firewall may be required. I won’t get too deep on how to make the SMTP server accessible from the Internet.
Once you have an SMTP Server that is reachable from the internet, you can create an “Connector” from the Exchange Online Admin Center.
Here are the steps:
1. From Exchange Online Admin, Access the Connectors feature via https://admin.exchange.microsoft.com/#/connectors
2. Click “Add a connector”
Note: This will be the IP address of the SMTP server that is handle e-mail for the on-prem SharePoint Server.
10. Complete the connector wizard to create the new connector.
Exchange Online is using an “address space” match when using this connector. So, when Outlook users send email to SharePoint folder, the email is delivered by the connector without the need of an MX record. This will work perfectly for email sent from your organization by Exchange Online. If you want SharePoint to receive email from public users over the internet, MX records will be needed.
Your SharePoint server only needs a location to the DROP folder. So, you don’t even need an SMTP Serer installed on the SharePoint server directly.
As stated, this configuration requires an SMTP Server exposed to the internet, please consider locking down access so only Exchange Online servers can access the SMTP Server. See: Office 365 URLs and IP address ranges – Microsoft 365 Enterprise | Microsoft Docs for a list of IP addresses to allow.
You are now able to continue using Exchange Online and your on-prem SharePoint servers and receive e-mail to Document libraries and Lists. I hope you found this Blog useful!