A quick Azure AD thread on adding custom domains This is pretty straightforward, but there are still some fun notes along the way Again, I really want this to be accessible to folks who have never even had access to Azure before, so please go sign up!
Did you know that you can get a free M365 E5 subscription with 25 user licenses to learn, create automation, and develop applications? I know most folks never get the chance to admin this stuff, so sign up now, and let's walk through this together :) developer.microsoft.com/en-u…
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7:12 PM · Jul 26, 2021

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First thing we're going to do is log into Azure AD and navigate to the Custom domain names section Shortcut: portal.azure.com/#blade/Micr… You should see your tenant domain name here (the onmicrosoft.com one), and you can click Add custom domain to start the process
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Type in the name of the domain you would like to add and click Add domain You need to have control of DNS for the domain - this is what stops us from stealing domains :p Azure AD generates a set of values for you to put in your DNS Copy the MS= value and go log into your DNS
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I host my DNS on Cloudflare for various reasons, don't judge... In the DNS section, create a TXT record, add the MS= content, and save the record Give a few minutes for replication, then head back to the Azure AD console and click Validate If it fails, wait and try again
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Once successful, you should now see your domain listed You can now use your domain as the UPN suffix (user@domain.com instead of user@domain.onmicrosoft.com) Existing users will need to be updated to use the custom domain if desired - just edit the user and change the suffix
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Important note: Exchange Online defaults all domains to Authoritative meaning email will give NDR's instead of using your MX record for your domain If you plan to host email elsewhere, set the domain to Internal Relay in the Exchange Admin Center and set up an outbound connector
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Replying to @NathanMcNulty
If you don't have a domain or DNS, you can have one domain per tenant for free: myo365.site/
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You are so kind! :)
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