The simplest way to do this without using anything fancy (such as extensive LINQ operations) may work this way:
Load the list into a DataTable
Get a list of distinct names from the email column - you could use Get Row Item to get all values of this column and then remove the duplicates .
For each name on this list, use the Lookup Data Table to filter records on the email column and fetch the records into another DataTable - this would be the email, name, subject and marks of a particular person
Use that DataTable as input to your email activity.
As I said, you could do this most likely in one or two steps using things such as LINQ, but that depends on how you want to approach the solution.