set -- a b c
echo $1 # should print a
echo $2 # should print b

IFS=":." # Will split on one or more of any of these characters.
VAR="1:2.3:.4:.:5"
set -- $VAR

echo $1 # Should print 1
echo $2 # should print 2

#!/bin/sh

SpamDir='/home/tay/spam'
WorkingDir='/tmp/spam-summary'

IFS=":"

# Loop on the files directly, instead of doing loops on line numbers
for FILE in ${SpamDir}/*.gz
do
        # Clear out variables
        From=
        To=
        Subject=
        Score=

        # ? What is column 9 on your ls -l ?
        ID=`ls -lh $Mail | awk '{print $9}'`

        # Your time functions look okay
        TimeEpoch=`ls -lh -D %s "$FILE" | awk '{print $6}'`
        TimeHuman=`date -r $TimeEpoch +"%Y-%m-%d %l:%M %p"`

        # Decompress file once instead of 9 times
        zcat "$FILE" > /tmp/$$

        # Read and process lines from the decompressed file one by one
        while read LINE
        do
                IFS=":" # Split on : so $1=X-Envelope-From, $2=<spammer@vnyu.com>
                set -- $LINE
                # If line has a : in it, save the header, then get rid of $1
                if [ "$#" -gt 1 ]
                then
                        HEADER="$1"
                        shift
                fi

                # Split on spaces, commas, and <>
                IFS="<>, "
                # Split <spammer@vnyu.com>, <whatever@...> into $1=spammer@vnyu.com, $2=whatever@..., etc
                set -- $1

                case "$HEADER" in
                X-Envelope-From) From="$From $@" ;;
                X-Envelope-To)     To="$To $@" ;;
                Subject)              Subject="$@" ;;
                X-Spam-Score)     Score="$@" ;;
                esac
        done < /tmp/$$

        echo
        echo "Processed $FILE"
        echo "To:$To"
        echo "From:$From"
        echo "Subject:$Subject"
        echo "Score:$Score"
done

rm -f /tmp/$$