add a customized button to the menu bar

[tungle]

Hi,
I'd like to add a button in the menu bar (right before the "Check for new message" button). The added button will open another php file in pop up window (basically not interfering with current working functions of the system). Which code files should I modify?
Tks.

[rosali]

You could this either by a plugin or by editing the template files (f.e. ./skins/default/templates/mail.html).