It seems it only works for the messages sent and received on this forum solution, not the imported ones. Note about sent messages: You have to hit "Go Advanced" before writing the reply and mark the box beside the "Save a copy of this message in your Sent Items folder" text to have your sent...
As to Myk's post about colours, I am not so much after a dark background, just not one that is bright white. We used to have a different tone on the background, but I don't really know which one that was.
I would really appreciate it if those of us who have issues with too bright backgrounds on both the reading and typing areas could have a less intense colour/shade. I know this is a work in progress, just posting a wish here.