What is the downside.. or issue, 
if one were to set up subdomains processing vs. regular domain processing?
example:
   companyzy1.domain.com
        emailuser@companyzy1.domain.com
        emailuser2@companyzy1.domain.com
 
   companyAbc.domain.com
        emailuserx@companyAbc.domain.com
        emailusery@companyAbc.domain.com
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I assume emails routes .. no big deal....
But more curious about chats, calendars....
'-------------
My assumption is that subdomains all would operate independently...
But then again, my assumptions  ... have made an 'a%%' of me before <grin>
Anyone having actual experiences.. with such, please advise.   
Thanks