If you send an email about a member of staff slagging them off?

Question

and then they go onto your computer and see that email, how do you legally stand?

Answer 1

Remember your Company PC belongs to the Company, not you - so if the other member of staff broke into your Company PC, and they have no authority to do so (for example, NOT your Manager and NOT a member of IT) then you should report them for illegal 'hacking' activity to the Company IT Dept. (get your story in first).

If you actually sent the email, be aware that the IT Dept keeps records & will be able to discover exactly when it was sent from your PC ( = you might be able to get away with claiming who-ever hacked you PC must have sent the mail, but watch out for timing .. it's no good blaming them for hacking today when the email was sent yesterday)

If you never actually sent it eg. all they saw was a 'draft' copy, then, of course, the 'draft' could have been intended to go to anyone with a similar name ... (deny deny deny deny ...)