Same here (on just using tweaked Thunderbird). I have used i think it was gvault or gmvault years ago, and it worked fine...But then I started using Thunderbird for actually managing my email (as a desktop email client).,..and then learned that one can set up maildir (so it is not a single mbox file), plus there are some offline settings within thunderbird...and it effectively did the trick of many of these automated methods...but i get the benefit of having a pretty good desktop client too. All i then have to do is ensure that the folder hierarchy of the maildir (as thunderbird saves the files and directories locally) is copied and backed up to a different location (per the ol' 3-2-1 backup strategy)...and i'm good; Thunderbird for the win!