I don't know about the "leave message on server" option. However, In Edit -> Account Settings -> -> Server Seetings, the option is set for "When I delete a message", "Move it to this folder" "Deleted on gmail".
I don't know about the "leave message on server" option.
However, In Edit -> Account Settings -> -> Server Seetings, the option is set for "When I delete a message", "Move it to this folder" "Deleted on gmail".