Type: boolean
Default: yes
Note: this option only affects maildir and MH style mailboxes.
When set, Mutt will check for new mail delivered while the mailbox is open. Especially with MH mailboxes, this operation can take quite some time since it involves scanning the directory and checking each file to see if it has already been looked at. If check_new is unset, no check for new mail is performed while the mailbox is open.