Yes it will work, for your current view of working. It's not the CNAME that breaks when you do this, it's all the other records.
You can't return a CNAME and something else. So your MX, NS, TXT, etc. records will be in an unknown state based on the client resolver/software. You'll see 40%-60% of your inbound email fail.
You can't return a CNAME and something else. So your MX, NS, TXT, etc. records will be in an unknown state based on the client resolver/software. You'll see 40%-60% of your inbound email fail.