I hope this will help you .....
just check with the square braces i hope this should work in your env
try to use {} in place of [] if it doesnt works
#!/bin/ksh
file1=/home/scott/a.txt
file2=/home/scott/b.txt
file3=/home/scott/c.txt
## -f is used for <file exists >
##verify whether there exist 3 files if it is true then send the files via attachement
IF [ ( -f $file1 ) -a ( -f $file2 ) -a ( -f $file3 ) ]
THEN
(uuencode $file1 $file1 ; uuencode $file2 $file2; uuencode $file3 $file3 ) |mailx -m -s "attachements"
a@aol.in
##verify whether there exist 2 files if it is true then send the files via attachement
ELIF [ ( -f $file1 ) -a ( -f $file2 ) ]
(uuencode $file1 $file1 ; uuencode $file2 $file2) |mailx -m -s "attachements"
a@aol.in
fi