What is the MX record for Office 365? There is no single value to copy. Microsoft builds a host for each domain, a token of its own followed by mail.protection.outlook.com, with a lower preference number than any other MX record, and some domains now get a host under mx.microsoft instead. Paste any address at your domain to see which form it publishes.
Only the domain is sent, to Cloudflare's public DNS resolver. The address stays on this page, and nothing is stored.
How to read the result
If the map names Microsoft 365, mail reaches Exchange Online, in either form. If it names a security gateway, a filtering service takes the mail first, and Microsoft may sit behind it where DNS cannot show it.
If it names your old host, or Google Workspace, that host still has the lowest preference number, so it still gets the mail. Senders try the lowest number first, as RFC 5321, the SMTP standard, sets out.
What to do next
Once mail flows to Exchange Online, Microsoft's DNS records reference for Microsoft 365 says to remove the MX records that point at your old system. A leftover record with a higher number fails nothing until the day Microsoft does not answer, which is why it is easy to forget.
The MX record decides where mail to your domain lands, replies included. Whether receivers trust the mail you send rests on SPF, DKIM and DMARC, so run the domain through the SPF record lookup next.
Checking which prospects run on Microsoft 365? Paste their addresses into the bulk MX lookup instead.