I think you could use Cypht... it's webmail that works like an aggregator for all your accounts... though you'd probably have to figure out a way to prevent the correlation of accounts based on IP, maybe using a VPN on that VM ot something like that
For anyone else looking at this, Cypht is another project I found that looks nice, but if you look into the install of it, they have some weird standards for leaving the source files outside of document root and making sure the web server only has read access to them for unexplained security reasons. Not quite sure what that's about, and it really doesn't lend well to our hosting setup, but I figured I'd list it as an option for anyone viewing this thread.