How to configure sendmail?

Hi.
Could you help me with sendmail configuration?

[root@Router MYVOLUME1]$ sendmail -f"sender@gmail.com" receiver@gmail.com < mail.txt
[root@Router MYVOLUME1]$ ps | grep sendmail
19362 root 4940 S sendmail: ./p2M9J4hl019360 gmail.com: user open
[root@Router log]$ cat /proc/version
Linux version 2.4.20 (kfurge@kfurge-laptop) (gcc version 3.0 20010422 (prerelease) with bcm4710a0 modifications) #44 Sat Jan 26 20:07:26 EST 2008

In syslog:
Mar 22 11:04:53 sendmail[19352]: gethostbyaddr(192.168.1.1) failed: -1
Mar 22 11:05:01 sendmail[19352]: p2M94re0019352: from=root, size=1, class=0, nrcpts=0, relay=root@localhost
Mar 22 11:05:20 sendmail[19354]: gethostbyaddr(192.168.1.1) failed: -1
Mar 22 11:05:22 sendmail[19354]: p2M95KMM019354: from=root, size=0, class=0, nrcpts=0, relay=root@localhost
Mar 22 11:19:04 sendmail[19360]: gethostbyaddr(192.168.1.1) failed: -1
Mar 22 11:19:04 sendmail[19360]: p2M9J4hl019360: from=sender@gmail.com, size=20, class=0, nrcpts=1, msgid=<201103220919.p2M9J4hl019360@Router>, relay=root@localhost