ACL/MAC Permissions for dovecot and postfix in CentOS 7

The key is here: failed: Permission denied (euid=1001(newusername) egid=1001(newusername) missing +w perm: /home/newusername, dir owned by 0:0 mode=0755

Dovecot is trying to write to /home/newusername/{whatever your maildir is} as newusername:newusername, however, the directory is owned by user 0:0 (root). Because the permission mode is 755, only the owner has +w permissions

Also, ensure that if you are using SELinux that your ACLs allow dovecot to write to your maildir