I cannot change password for the email accounts - it takes me to the page with details of control panel.
The are two users with the same email addresses
"email@example.com" under the corresponding subscription, Users tab.
The issue was caused by the migration from old Plesk versions, two users with the same email addresses were created.
You should remove one of the users:
If email account should be used by subscription owner, remove Mail User
"firstname.lastname@example.org"first, then go to:
Users > Subscription Owner > Change Settings > Create an e-mail address under your account
and specify required account name:
If email account should not be used by subscription owner and should exist as separate account, go to:
Users > Subscription Owner > Change Settings > Use an external e-mail address
and set another email address.