I was not using my Linux box at the time in these message logs in maillog. How can I figure out what these are?

Apr 30 04:02:03 localhost sendmail[6442]: h3UB23Gn006442: from=root, size=1187,
class=0, nrcpts=1, msgid=<200304301102.h3UB23Gn006442@localhost.localdomain>, relay=root@localhost
Apr 30 04:02:03 localhost sendmail[6445]: h3UB23p5006445: from=<root@localhost.localdomain>, size=1493, class=0, nrcpts=1, msgid=<200304301102.h3UB23Gn006442@localhost.localdomain>, proto=ESMTP, daemon=MTA, relay=localhost.localdomain [127.0.0.1]
Apr 30 04:02:03 localhost sendmail[6442]: h3UB23Gn006442: to=root, ctladdr=root
(0/0), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30051, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (h3UB23p5006445 Message accepted for delivery)
Apr 30 04:02:05 localhost sendmail[6446]: h3UB23p5006445: to=<root@localhost.localdomain>, ctladdr=<root@localhost.localdomain> (0/0), delay=00:00:02, xdelay=00:00:00, mailer=local, pri=31730, dsn=2.0.0, stat=Sent
Apr 30 04:07:09 localhost sendmail[6652]: h3UB79n0006652: from=root, size=427, class=0, nrcpts=1, msgid=<200304301107.h3UB79n0006652@localhost.localdomain>, relay=root@localhost
Apr 30 04:07:10 localhost sendmail[6654]: h3UB79p5006654: from=<root@localhost.localdomain>, size=715, class=0, nrcpts=1, msgid=<200304301107.h3UB79n0006652@localhost.localdomain>, proto=ESMTP, daemon=MTA, relay=localhost.localdomain [127.0.0.1]
Apr 30 04:07:10 localhost sendmail[6652]: h3UB79n0006652: to=root, ctladdr=root
(0/0), delay=00:00:01, xdelay=00:00:01, mailer=relay, pri=30254, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (h3UB79p5006654 Message accepted for delivery)
Apr 30 04:07:10 localhost sendmail[6655]: h3UB79p5006654: to=<root@localhost.localdomain>, ctladdr=<root@localhost.localdomain> (0/0), delay=00:00:00, xdelay=00:00:00, mailer=local, pri=30947, dsn=2.0.0, stat=Sent

Probably something like logwatch and others!

su to root, type mail --help to learn the commands within mail. Then type 'mail' and read the messages.