email validation: verify only MX, with a 7s timeout (#43422)

wcs/qommon/form.py

@@ -44,7 +44,6 @@ except ImportError:
 
 try:
     import DNS
-    DNS.ParseResolvConf()
 except (ImportError, IOError):
     DNS = None
 
@@ -900,21 +899,15 @@ class EmailWidget(StringWidget):
                 except UnicodeError:
                     self.error = _('invalid address domain')
                     return
-                # simply lookup host name; note it will fail if hostname
-                # doesn't have an A entry
-                try:
-                    socket.gethostbyname(domain)
-                except socket.error:
-                    # will fail on lack of DNS module or MX lookup failure
+                if domain == 'localhost':
+                    return
+                if DNS is not None:
+                    DNS.ParseResolvConf()
                     try:
-                        l = len(DNS.mxlookup(force_str(domain)))
-                    except:
-                        l = 0
-                    if l == 0:
+                        if not DNS.mxlookup(force_str(domain), timeout=7):
+                            self.error = _('invalid address domain')
+                    except DNS.DNSError:
                         self.error = _('invalid address domain')
-                else:
-                    # and then, localpart could be tested
-                    pass
 
 
 class ValidationCondition(Condition):