Adam Gazzaley and Larry Rosen bluntly summarize in their 2016 book, The Distracted Mind:

A 2012 McKinsey study found that the average knowledge worker now spends more than 60 percent of the workweek engaged in electronic communication and Internet searching, with close to 30 percent of a worker’s time dedicated to reading and answering e-mail alone.

I recommend you file in bulk and use a full-text search engine to find your mail; use topic filing with folders or tags only if absolutely necessary. I also recommend you turn off e-mail notifications and then check e-mail no more frequently than every two to three hours; avoid getting trapped in e-mail all day.