users: Show "Service Unavailable" error if the mail server is unreachable
users: Show "Service Unavailable" error if the mail server is unreachable

.. instead of crashing with an unhandled exception

TobiasLohner/SkyLines,Turbo87/skylines,kerel-fs/skylines,kerel-fs/skylines,kerel-fs/skylines,Harry-R/skylines,RBE-Avionik/skylines,Harry-R/skylines,shadowoneau/skylines,shadowoneau/skylines,Turbo87/skylines,snip/skylines,skylines-project/skylines,dkm/skylines,dkm/skylines,Turbo87/skylines,RBE-Avionik/skylines,Turbo87/skylines,snip/skylines,RBE-Avionik/skylines,RBE-Avionik/skylines,TobiasLohner/SkyLines,Harry-R/skylines,skylines-project/skylines,skylines-project/skylines,dkm/skylines,snip/skylines,TobiasLohner/SkyLines,shadowoneau/skylines,skylines-project/skylines,shadowoneau/skylines,Harry-R/skylines,dkm/skylines