Single paid user account: hosting multiple domains each with their own separate IMAP inbox?

Single paid user account: hosting multiple domains each with their own separate IMAP inbox?

Today, I have paid for an upgrade to the Standard 10GB plan, because I need to use multiple email domains that I own, all with IMAP. As I am a single person with multiple email domains, I paid for only a single user on the Standard plan.

I need each domain to have ITS OWN INBOX; consolidating the emails from all domains into a single inbox is neither  acceptable for me nor my country's business laws. 

As an illustration, I would like the following email folder structure:
  1. me@zoho.com   (my Zoho user account)
  2.   |
  3.         me@mydomain1.com
  4.             INBOX
  5.             <folders>
  6.   |
  7.         me@mydomain2.com
  8.             INBOX
  9.             <folders>

Is this possible? 

I have searched the forums, and the most applicable support answer that I found was to add another user, which would cost me more money.

Has anybody solved this type of issue?

This is a deal-breaker for me.