+1 Alan!
First I had the "no mails at all" bug, then, until today, this "double mails" bug.
User's workaround and fix for the former: Chance your mail address back and forth a few times, until it eventually works.
User's workaround for the latter: Be glad to receive the honour to get mails, and kindly accept the double ones.
There are nastier bugs around, like the "cannot re-equip necessary equipment (like putters) after a rental". This one makes it impossible to play and has been in duty for some months!