You should be able to insert the Tiger disk and when the window opens showing the Install Mac OS X icon, scroll the window until you see the Optional installs.mpkg. Doube click that, then click on the box next to Applications, then click on only Mail. It should then only install Mail and nothing else. Graphics that show the steps are in the first link in my previous post.
If that doesn't do the trick you could always use Pacifist but I don't know if they have a free trial.
https://www.charlessoft.com/pacifist_olderversions.htmlAs to repartitioning, yes, just changing from two to one partition via that command will erase all data. But there is a way to eliminate one partition, then resize the other (first partition) to add the space from the second partition. Eliminating the first creates a problem whereby you need to copy the data to another source, then reformat and copy the data back.
Here is the way to eliminate the second partition and add space to the first :
http://www.macworld.com/video/30601/delete...osing-data.htmlIt can also be done by Terminal though I doubt you want to go that route.
But if you follow the first path with just installing Mail from the Optionals package, it won't need a lot of space, just what Mail takes up.