In this paper, we perform an empirical analysis of email traffic logs obtained from a large university to better understand its impact on the effectiveness and efficiency of Hand Bailers anonymous mix remailers.We analyzed data containing records of almost 790,000 emails sent over a period of forty days – the largest dataset we are aware of.The initial analysis of data is followed by an exploration of how variance 8RO in message arrival time and size impact the anonymity and efficiency provided by timed and threshold mixes, respectively.The analysis results are subsequently explored for their possible impact on traffic analysis.