Complex sentence: Additionally, nearly 2,100 emails on the server were retroactively marked as classified by the State Department that were not marked as classified at the time they were sent, including 65 emails deemed "Secret" and 22 deemed "Top Secret".
Split into simpler sentences: Additionally, nearly 2,100 emails on the server were retroactively marked as classified by the State Department that were not marked as classified at the time they were sent. This includes 65 emails deemed "Secret" and 22 deemed "Top Secret".