Yes, you can.
In order to do this, cancel the initial connection window when opening your email
application. This will stop you from dialling Virgin Media and will stay off-line
until such a time when you click to check for email.
Sometimes you may need to cancel the connection box a
number of times. This is because the email being previewed requests a
connection to download its content. This can be annoying if the email contains 30 pictures, as it will ask you 30 times to connect as it tries to download the pictures. Unfortunately there is no easy way to close the connection
box.