RedHat installs all it's packages via RPMs or SRPMs. SRPMs intall with source. I'm going to guess that Mandrake is much the same. You won't find an RPM version of sendmail because both distros configure the install to work with their own system. The problem with having to mount and unmount manually is a fact of life we may have to live with. My system will automount when I pop in a CD but somtimes will not let me eject with the button unless I unmount it manually first. You might try to have amd start at bootup to see if this changes for you. AMD is an automount deamon that will will try to load devices when it gets a signal. You might also want to check /etc/fstab to see if you have your cd-rom defined something like the following:
LABEL=/ / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /proc proc defaults 0 0
none /dev/shm tmpfs defaults 0 0
/dev/hda3 swap swap defaults 0 0
/dev/cdrom1 /mnt/cdrom1 iso9660 noauto,owner,kudzu,ro 0 0
/dev/fd0 /mnt/floppy auto noauto,owner,kudzu 0 0
/dev/cdrom /mnt/cdrom iso9660 noauto,owner,kudzu,ro 0 0
I have both a dvd and cd-rw so that's why I have a cdrom and cdrom1. When you reboot and amd loads, you will get an error saying no mount points defined. This is normal. It's just saying there is nothing in the floppy or cd drives. If you have a Disk Manager in your systems menu, I would create a launcher for it in the launch panel so you can get to it faster if you have to mount or unmount a device. Getting back to your sendmail install error, I think it doesn't like your kernal.