in cPanel some email accounts suddenly disappeared. Folders for email accounts did not disappear, they do exist in /home/username/mail and all the information was there
you notice that one or more email accounts have gone missing here is how to fix this
restore this file from backups
if you do not have backups, open /home/user/etc/domain/shadow file with an editor on your own option. copy one of the entries to recreate the entries for your missing email accounts.
Emails are still disappeared in cPanel
mv /home/user/.cpanel/email_accounts.json /home/user/.cpanel/email_accounts.json.backup
reset the passwords of missing emails