(In final development) 

Yes, you'll observe duplicates of all "configured pop email accounts" appearing beside the sub-domain, and or all sub-domains you've created.  

Now we know you'll be tempted to use (what appears to be) a perfectly good email address, BUT please "Don't!"  

This is a feature that is in final development. 

While it may look somewhat confusing at first glance, it's really not.  In the near future, you'll be able to configure these email accounts for use with your sub-domains.  

For example, if you configured: 

support.yourdomain.com,

then you'll be able to use the address:

mailto:tom@support.yourdomain.com.  

For the time being, please configure email address's that correspond to your standard  "top-level" domain, and just ignore the sub-domain duplicates.