Turned my computer on this morning and I have lost everything in my email box

all that is there is emails from 17.30 yesterday to now as they had not been downloaded from the server

I have read a few posts about this and tried a few things suggested but I can not seem to find anything anywhere

I started windows mail up then it rebooted itself for some reason and everything had gone

any help I would be hugely grateful

running windows 10 if that is important

Thank you