How do I keep my emails private?

[Traveler]

I have the window pop up where I must fill in email address and password, but
even if you close that and not fill in the blanks one can still open my
email. This is on my laptop, but I do not have this problem on my home
computer. How do I keep my emails from being read by others?

 

[epping]

is this a work email account, if so authtication is done via active directory
i.e. when you log on to the network (no further password is required)

 

[Traveler]

This is my personal computer, my laptop. When I open Microsoft Outlook there
is a security pop up with email and password but if someone else was using my
computer they can still read and respond to my email, while the "security"
pop up window is open. Even without using the password or email address
anyone can still read my email. I do not have this problem on my normal
computer.