if you are looking at simply indexing a CSV file there are other ways to do so, and make the fields a key/value pair as well. That could not get accomplished with simply indexing an email attachment.
You could have a file directory on your splunk waiting to index any file in it, and put file there via FTP, or a custom python script.
Here is an example for importing csv files:
inputs.conf
[batch:///tmp/file.csv]
sourcetype=MINE
move_policy=sinkhole
props.conf
[MINE]
INDEXED_EXTRACTIONS=CSV
FIELD_DELIMITER=,
FIELD_QUOTE="
HEADER_FIELD_LINE_NUMBER=1
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