Office 365 – How can I send an email from a vendor-hosted application using a UNC custom domain?

This document explains how you can send mail from a vendor-hosted application or system using a custom domain without triggering Office 365’s anti-spoofing system.

Decide on the domain name from which you want to send. For example, the domain name for is “”.

Check in DNS to see if that domain is in use, and what attributes it has, by going to a command prompt and typing:

Set type=any

If there is no domain with the name you have chosen, and no TXT record that conflicts with your request, open a Help Request with ITS Networking requesting the domain be created in DNS.

Networking will have you sign a Memorandum of Understanding (MOU) as part of the process (Note: you may scan and upload the signed MOU to the Help Request).

Also ask Networking to create a TXT record in DNS for the domain. Include the SPF record that your vendor wants you to use. It will look something like this:

“v=spf1 ?all”


Don't See Your Question Here?
Check out UNC's Office 365 Migration site. There are a lot of resources to help you become familiar with Office 365.

Check out Microsoft's FAQs for Office 365 ( Microsoft also has some great training videos you can watch to become familiar with using Office 365 applications. Please visit the Office Training Center.