I've got a gmail account and altered the settings to be like yours as I usually use 'Move it to the gmail Trash' I also changed my double click settings from opening in tab to new window. I also selected to close window upon move or delete. I found opening in a new window worked ok. delete marked email in list with a line. Window did not close upon delete. email selection did not auto advance I use 'Move it to the gmail Trash' as I want deleted emails to be fully removed some server and not just a label removed. Generally I read opened emails in the Message Pane open in a new tab for double click upon delete the opened tab closes and email selection advances to show next email in Message Pane. So all works as expected for me using those settings. Your issue sounds like this bug report: https://bugzilla.mozilla.org/show_bug.cgi?id=452394