[FIX] Email validation (#4730)

Patches #4726, not in a great way, I'd rather use a well-defined regex but I could not get that to work and this is blocking someone, so this will do not for now.

utils.py

@@ -177,7 +177,7 @@ def version():
 
 
 def valid_email(s):
-    return bool(re.match(r'^(([a-zA-Z0-9_+\.\-]+)@([\da-zA-Z\.\-]+)\.([a-zA-Z\.]{2,6})\s*)$', s))
+    return bool(re.match(r'^(([a-zA-Z0-9_+\.\-]+)@([\da-zA-Z\.\-]+)\.([a-zA-Z\.]{2,10})\s*)$', s))
 
 
 @contextlib.contextmanager