search_mail_address.dart

String mailPattern = r"^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,253}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,253}[a-zA-Z0-9])?)*$";
RegExp regEx = RegExp(mailPattern);

String mailAddress = "Couldn't find any mail in the foto! Please try again!";
for (TextBlock block in visionText.blocks) {
  for (TextLine line in block.lines) {
    if (regEx.hasMatch(line.text)) {
      mailAddress = line.text;
    }
  }
}