[Jenkins]

keep getting names email address like these register. any suggestions on preventing this? I'm currently using question/answer system. Or a way to "bulk delete" usernames? deleting these one by one is painful.

gunnozo74 sa.n.t.o.m.c.i.n.t.o.s.h6.52@gmail.com 09-23-2010 09-23-2010 0
gentomi34 sa.n.to.m.ci.ntosh.6.52@gmail.com 09-22-2010 09-22-2010 0
pakuide42 s.a.n.t.o.m.c.i.nt.o.s.h6.52@gmail.com 09-22-2010 09-22-2010 0
yusenshi81 san.to.mc.i.n.t.osh.652@gmail.com 09-21-2010 09-21-2010 0
pusashin127 sa.ntom.c.i.nt.o.s.h.6.52@gmail.com 09-21-2010 09-21-2010 0
kansen45 s.a.ntomc.in.to.s.h.652@gmail.com 09-21-2010 09-21-2010 0
zugumie184 sa.nt.o.mc.i.n.t.o.s.h652@gmail.com 09-20-2010 09-20-2010 0
zuihibi131 s.ant.o.mcin.t.osh.6.52@gmail.com 09-20-2010 09-20-2010 0
betaido152 sant.om.c.i.n.t.o.s.h6.5.2@gmail.com 09-20-2010 09-20-2010 0
kanpatsu174 san.to.mci.nt.os.h652@gmail.com 09-20-2010 09-20-2010 0
ginhoke0 s.a.ntomc.i.n.t.osh.652@gmail.com