temp and mail.queue become large size exchange 2013

Hi Team,

I have two CAS, and two MBX Exchange 2013 CU4/SP1. when i checked my temp and mail.queue become large. mail.queue 60 GB and temp around 45 gb.

my question are, how come the mail.queue is so large in size?

can i stop the growing? how about the temp file, is the temp file safe to delete? :)

regards