[TYPO3-mvc] validate domain object in own validator

[Domi]

Here the output of <f:debug> inside of the <f:form.error> loop:

array (2 items)
    settings => array (8 items)
    error => Tx_Extbase_MVC_Controller_ArgumentErrorprototype object
          message => 'Validation errors for argument "client"' (39 chars)
          code => 1245107351 (integer)
          propertyName => 'client' (6 chars)
          errors => array (3 items)
             0 => Tx_Extbase_Validation_Errorprototype object
                   message => 'User with this email already exists' (35 
chars)
                   code => 99988776 (integer)
             interestCountries => 
Tx_Extbase_Validation_PropertyErrorprototype object
                   message => 'Validation errors for property

"interestCountries"' (50 chars)
                   code => 1242859509 (integer)
                   propertyName => 'interestCountries' (17 chars)
                   errors => array (1 items)
                      0 => Tx_Extbase_Validation_Errorprototype 
objectmax depth
(...)

Instead of the property name "email" the error has "o" as identifier and 
only the message and code, I want that the error gets assigned to the 
"email" property of my domain model.

Hope someone can help me out.

THX
Dominic