Fortunately the most common mail folder format, Mbox, is very simple and basically consists of just the emails pasted one after another with a line beginning with 'From ' as the separator so one could copy the email body & headers from the HTML source code of those web pages, paste them in and add MIME type headers to tell the email client that email body is in HTML.
Unfortunately the dates & addresses in the headers are in the wrong format for emails so those will need conversion too.
That would be tedious to do manually for a few emails let alone thousands.
Repeated clicking ' An anonymous visitor to this site kindly provided an updated version to work with GDS 5.7.
It requires one more step as it starts from the GDS timeline page rather than the home page but otherwise operates the same.
How to use it: I used the Mozilla Thunderbird variant of Mbox as most email clients can import that (for Thunderbird itself, just copy the file into the directory Thunderbird is using for email folder files and restart Thunderbird).
Unfortunately lousy M$ Outlook 2k is one that can't (although I've read that it might be possible via M$ Outlook Express). I don't know the full range of possibilities from GDS (e.g.
Occasionally files may accidentally be deleted or corrupted or a storage medium may fail.