Setting up your domain to work with Office 365 operated by 21Vianet can be challenging. There are lots of detailed steps to go through on different sites, and the DNS system is nitpicky to work with. And the DNS setup for your domain affects important business activities, like email! But we can help you fix issues with your domain's DNS setup. For example, the domains troubleshooter will show you any records that need fixing, and exactly how to fix them.
If you’ve run into problems after adding your domain, start by making sure that the DNS records for your custom domain are set up correctly by checking the domain in your account in Office 365:
Sign in to Office 365 with your work or school account.
Choose Setup > Domains.
Choose the domain that you're working with, and then, on the right side, choose Find and fix issues. If any DNS records are set up incorrectly for Office 365, the domains troubleshooter will identify them and show you the correct entries you should use.
If you've fixed any DNS issues and you're still having trouble using Office 365 services with your domain, try the following.
You can't update your A record or CNAME record to point to your website: Update custom DNS records in Office 365