I'm extremely confused about this. I have an older Kindle Paperwhite (PW 3/ 7th gen I think?) and when I used the 'email sent' feature I got that mail about dropping mobi support in favor of epub, but when sending an actual epub I got an error for sending a wrong file, ostensibly because the Kindle only supports mobi.
Are they going to ship a software update? Would be a shame if that service doesn't work any more in the future.