v1.0.5 and v1.0.8. The successors needed Gnome 2 and I wasn't about to go there. For my machine, the details are:
72 MB in the Inbox (260 msgs), 73 in a sub folder (204 msgs). This now seems rather odd. Some of the messages did include rather large image attachments, but those don't account for the above numbers. The index files are similarly bloated.