Cpanel control panel is going to remove its popular webmail NeoMail from the list of webmails it offers. Presently Cpanel provide

Neomail
Horde
SquirrelMail

Neomail is popular amoung many users as it is easy to use and first button to click after you login to webmail. I have been using cpanel for years, never clicked other two webmail buttons for reading a mail.

Cpanel currently use mbox format to store mails, this is not reliable mail storage format, so they are switching to Maildir format orginally created by qmail author. Exim and many other mail servsr support Maildir mail storage format.

Here is some reason for moving to Maildir storage format.

And what happended was many customers are popping their mailboxes every so often and sometimes they took a minute and more to download contents of their mailboxes. In this case, there’s high chance that next time exim runs, it won’t be able to grab the lock again, and mails are pending in the queue.. with
1.5x incremental delay time, so on and so on. We saw quite a number of mail get delayed in this manner for a day or so. Natuarally, I guess those mails got delivered during the night.

To switch to Maildir format need reconfirgration to exim mail server to store emails in Maildir format, also webmail that support Maildir format. Neomail do not support this, so will be removed from Cpanel.