MBox is the quick and ancient format for collecting mail on Unix systems, it consists of a single file per user under /var/spool/mail that has messages concatenated. Performance is very weak when deleting messages from a big mail store as the entire file has to be rewritten.
Maildir was invented for Qmail by Dan Bernstein and has a single message per file providing fast deletes among other performance profits. Maildir mail space speeds up the functionality of the mail server and overcomes memory usage due to mail-related processes. Multiple processes can use mailers at the same time.
It is time to change Mbox accounts to Maildir on your cPanel server.
convert mbox to Maildir
How to Convert MBox accounts to MailDir cPanel
- The reformation process may take up to 24 hours. This depends on your server’s hardware and the number of accounts to convert.
- You cannot send or receive mail while the server is in the turning process. Try to run this process at an off-peak time.