Before you try to install and dual boot it is very important to understand the concept of "what boot mode your BIOS is in" and "what mode you booted the installer to".
Then follow the example of Linux Mint (but most Linux installers are very similar)to carefully understand WHERE you are installing your Boot Loader to whether that be MBR or EFI.
How Am IBooted?
First it's important to check your BIOS to see........
This actually only happened after an e-mail server ran out of space due to run away log files. Normal Desktop clients were not affected. It appeared to be a bug in K9 mail but even reinstalling/wiping all settings did not fix it (read e-mails would still not reappear).
This is moreso a bug in Dovecot where it probably messes up the index files.
How do you fix this in Dovecot/your e-mail server?
You need to delete the do........