I was surprised to not see a feature request here to be able to change the email address associated with our Kasa accounts.  It's been requested many times in the forums and elsewhere with MANY folks asking for this.  When you have many devices, groups, schedules, etc., it is incredibly painful to use the current process: deleting devices from the app, resetting each device to factory settings, logging the app into a new account, and re-adding all of the devices, groups, schedules, etc. 

The email address I currently use gets so much spam that I have moved to a new one.  But I'm hanging onto the old one simply because my Kasa devices are mapped to it and I've been dreading taking the time to move them all.  Nearly every other web site/app I use has the ability to change the email address associated with the account.  It's just something must customers just expect to be there.

I would like to suggest that you should always make the following suggestion to customers BEFORE setting up their devices: 

         *** Create a new free email address that is associated with the residence rather than a person (e.g. FiveSouthStreet@gmail.com).  Then use this email address when you initialize the Kasa app and add devices to it.  You can of course then use the email address for any other smart home or IoT devices you have. 

Doing this will make it 1) less likely that this email will get compromised/spammed if it's only used with a few web sites/apps and 2) easy to turn over the email address/password to a new owner should you move and leave the devices behind.