Use better handling for missing

* Using better handling for missing, does not conflict if the username contains "missing"
4 jobs for user-checkmail in 1 minute and 11 seconds (queued for 1 second)
Status Job ID Name Coverage
  Lint
passed #1499
lint:lint-php5.4

00:00:42

passed #1500
lint:lint-php5.6

00:00:40

passed #1501
lint:lint-php7.0

00:00:40

 
  Codesniffer
passed #1502
codesniffer

00:00:29