Issue :
All email accounts were accessible via the main email account for that domain but now they aren’t.
Fix :
E-mail access from the main account to individual e-mail accounts is provided by symbolic links (symlinks) within the cPanel user account’s mail directory which link to the directory of each individual e-mail account. To restore or re-create these, use the following built-in cPanel script :
/scripts/linksubemailtomainacct