add also a check with a +, which triggers an invalid email on the routing side

tests/socket-proxy/tests.yml

@@ -386,6 +386,11 @@ exim_mail_over_quota_wrong:
   user: 'exim'
   query: 'over_quota:nosuchuser@example.com'
   expected: 'false'
+exim_mail_over_quota_wrong_with_plus:
+  host: 'mailrelay'
+  user: 'exim'
+  query: 'over_quota:nosuchuser+foo@example.com'
+  expected: 'false'
 ## mail_forward
 exim_mail_routing_mail_forward:
   host: 'mailrelay'