I'm having some problems with email relay setups to smtp.office365.com. Specifically, I have two scenarios: the first involves MFPs (Multifunction Printers)/Copiers that have been configured to send emails directly to smtp.office365.com for years, and the second is a relay server that's also been sending directly to the same address without issues. However, the MFPs/Copiers suddenly can't send emails at all, while the relay server continues to work fine. They are both on the same network and behind the same firewall/IDS/IPS. My suspicion is that the relay server is more persistent and keeps trying to send, while the MFPs/Copiers only make one attempt before giving up. When I switch the MFPs/Copiers to a different gateway that doesn't enforce geo-blocking, the emails go through just fine. However, I've checked the nslookups for smtp.office365.com and the responses are always US-based IPs from both network segments. Does anyone have any suggestions?
4 Answers
Make sure your MFPs or Copiers are set up to use OAuth. Double-check the account they're using as well. Ensure SMTP Protocol is enabled in Exchange Online and the 'Send As' option is activated if the sender email differs from the login account. You can find details here: [Mailbox Permissions](https://learn.microsoft.com/en-us/microsoft-365/admin/add-users/give-mailbox-permissions-to-another-user?view=o365-worldwide).
Honestly, just use SMTP2GO for everything and simplify your setup. Microsoft is making it difficult to relay emails through their platform, so it might be better to use a dedicated service.
You might want to consider setting up an IP address-based connector for SMTP relay. It could help you avoid any authentication headaches, especially if your MFPs or Copiers don't support modern authentication. Here’s a link with some guidance on how to do that: [Set Up an IP Address-Based Connector](https://learn.microsoft.com/en-us/exchange/mail-flow-best-practices/how-to-set-up-a-multifunction-device-or-application-to-send-email-using-microsoft-365-or-office-365#configure-an-ip-address-based-connector-for-smtp-relay).
We’ve attempted to use relay connectors for copiers but had mixed success. Typically, we just set up a generic Gmail account for each customer and create an app password for the copier. This method avoids a lot of hassle, and if the Gmail password changes, we just regenerate the app password if needed. Occasionally, new Gmail accounts can be flagged as spam initially, but you can submit an unblock request if that happens.
This is how we've always managed it, and it eliminates worries about authentication or MFA... a real lifesaver!