Overwrite Labels and Validation messages

You can overwrite any label in powermail via TypoScript Setup. Have a look into locallang.xlf (EXT:powermail/Resources/Private/Language/locallang.xlf) for getting the relevant keys, that you want to overwrite (e.g. validationerror_mandatory).

plugin.tx_powermail {
    _LOCAL_LANG.default.validationerror_mandatory = Please insert a value
    _LOCAL_LANG.de.validationerror_mandatory = Bitte Pflichtfeld ausfüllen
}