Depends on the network and the laptop. Anything going over the network is easily intercepted unless its encrypted. If your laptop isn’t configured properly they can gain access to your disk drive.
Say you log into email and read them. They’ve captured your login/password and the contents of the email.
All wireless networks can be hacked using free software.
Most email applications use SSL connections (https://). That means that your whole email session, including the login/password process is encrypted between your computer and the destination computer.