i found a solution,
i edited the file ...\roundcubemail-1.0.2\skins\classic\includes\messagetoolbar.html and i deleted following code lines
...
<roundcube:button command="delete" type="link" class="buttonPas delete" classAct="button delete" classSel="button deleteSel" title="deletemessage" content=" " />
...
...
<roundcube:button command="move" type="link" class="buttonPas move" classAct="button move" classSel="button moveSel" label="move" title="moveto" content=" " data-menu-pos="bottom" />
...
the move button no show and the user will not be able to move messages to the trash
the disadvantage is that i need to edit the file messagetoolbar.html in each skin folder and to all accounts the move button is disabled
I still do not know if activating plugins the user can see the move button