Have you ensured that you have selected the radio button just underneath the email. Circular radio button is meant for marking the email address as ‘primary’. However, it should have been selected by default, whenever you seek to create a new lead.
I can confirm that I’m having the same issue with Leads and Accounts after upgrading to 7.7.7.
It seemed to be a JavaScript issue, If you clear your web browser cache it seems to work. Unfortunately for myself this wasn’t an option I could rely on, If anyone could provide a more elegant resolution, I’d love to hear.
I upgraded from 7.7.5 to 7.7.8 and the same issue happens.
In addition to emails not being saved if I change any users email (click any of the radio buttons) and try to save it the previous email also gets removed from the user details.
I am using SuiteCRM on Windows with MSSQL