Non-separation of Accounts

I and my wife have a joint account and, in addition, she has a personal account. In eM Client  the messages addressed to the joint account are listed in both accounts; but any message addressed to my wife’s account does not appear at all. This is obviously wrong, and should surely be put right. .

Each account will have its own set of folders, unless you are using POP3 and specified in the setup that they should use a common folder tree.

How many email accounts have you setup in eM Client?

Are you maybe looking in the Smart Folders, which has a combined Inbox for all accounts?

Can you provide a screen shot of your folder three indicating where you are seeing the combined messages?