VegaS

main_dict = {}
for email, category, value in main_list:
    token = (email, category)
    if token in main_dict:
        main_dict[token] += int(value)
    else:
        main_dict[token] = int(value)

main_list_converted = []
for k, v in main_dict.iteritems():
    main_list_converted.append(list(k) + [v])

main_list_converted.sort()

"""
for item in main_list_converted:
    print (item)

[['user1@test.com', 'Administration', 100]
['user2@test.com', 'Development', 170]
['user2@test.com', 'Testing', 30]
['user3@test.com', 'Administration', 95]
['user3@test.com', 'Development', 400]
['user3@test.com', 'Testing', 200]]
"""