My problem: Updated TYPO3-Installation from Vs. 8 to 12. The tx_form forms works fine but only with the ascii subset of characters in the fields. If any user fills the form fields with umlauts or other special characters the mails are sent but contains no content for this field (HTML) or *** characters in text mails.

No special form is used but simply the possibilites of the form editor in the backend.

Any ideas?