diff -ur admin.o//handlers/dns/forward_zone.py admin/handlers/dns/forward_zone.py
--- admin.o//handlers/dns/forward_zone.py	2011-10-13 10:08:22.000000000 +0200
+++ admin/handlers/dns/forward_zone.py	2011-10-13 09:29:52.000000000 +0200
@@ -58,7 +58,7 @@
 	'zone': univention.admin.property(
 			short_description=_('Zone name'),
 			long_description='',
-			syntax=univention.admin.syntax.string,
+			syntax=univention.admin.syntax.dnsZone,
 			multivalue=0,
 			options=[],
 			required=1,
diff -ur admin.o//syntax.py admin/syntax.py
--- admin.o//syntax.py	2011-10-13 10:08:43.000000000 +0200
+++ admin/syntax.py	2011-10-13 10:05:28.000000000 +0200
@@ -1027,6 +1027,22 @@
 			return text
 		raise univention.admin.uexceptions.valueError,_("The name of a reverse zone consists of the reversed subnet address followed by .in-addr.arpa. Example: \"0.168.192.in-addr.arpa\"")
 
+class dnsZone(simple):
+	_re = re.compile(r'^[a-zA-Z0-9](:?(:?[a-zA-Z0-9-]{0,63})*\.?)*[a-zA-Z0-9]$')
+
+	@classmethod
+	def parse(self, text):
+		if text is None:
+			raise univention.admin.uexceptions.valueError(_("Missing value!"))
+		if len(text) >= 255: 
+			raise univention.admin.uexceptions.valueError(_("Value may not be longer than 255 chars!"))
+		if self._re.match(text) is not None:
+			return text
+ 		elif max(map(len, text.split('.'))) >= 63:
+			raise univention.admin.uexceptions.valueError(_("Value may not longer than 63 chars between dots!"))
+
+		raise univention.admin.uexceptions.valueError(_("Value may not contain other than numbers, letters and dots and may not end with a dot!"))
+
 class dnsName(simple):
 	_re = re.compile('^[a-zA-Z0-9][a-zA-Z0-9._-]*[a-zA-Z0-9.]$')