I'm moving my web host from GoDaddy to Azure, and I'm getting the error above.
These are the steps I followed:
1) Made my azure website the paid (yet shared) version
2) Went to GoDaddy and changed A record to @ 18.104.22.168 (shared server ip)
3) Under CNAME entered "www" in the CNAME column, and "mysite.azurewebsites.net" in the 'points to' column.
www.mysite.com goes to the IP, but it does not find my site so I get the 404. Did I neglect to do something?
I did confirm the CNAME is mysite.azurewebsites.net at mxtoolbox.com.
Solution: There is a step 4. In Azure under Manage Custom Domains I needed to add my www.mysite.com. Worked instantly.