grandfathering old systems note

README.md

@@ -26,6 +26,12 @@ sudo make install
 
 User of Arch-based distros can also install mutt-wizard from the AUR as [mutt-wizard-git](https://aur.archlinux.org/packages/mutt-wizard-git/).
 
+*NOTE:* If you have used an older version of mutt-wizard, especially when it used to use `offlineimap`, you need to remove your old configs. Back anything up that's important and run:
+
+```
+rm -rf ~/.config/mutt ~/.msmtprc ~/.config/msmtp ~/.offlineimap ~/.offlineimaprc ~/.config/offlineimap ~/.mbsyncrc
+```
+
 The mutt-wizard is run with the command `mw`. It also installs the `mailsync` command. Once everything is setup, you'll use `neomutt` to access your mail.
 
 - `mw add` -- add a new email account