grep with equivalent performance? i highly doubt that. my mailbox has 2.6M emails: running grep through millions of files if you use maildir or a similar format

grep with equivalent performance? i highly doubt that. my mailbox has 2.6M emails: running grep through millions of files if you use maildir or a similar format takes forever. likewise running grep on a 7.6GB large mbox file takes more than a minute. on the other hand in supmua (which inspired notmuch) the same search takes seconds.