Email per day - mental practitioner

How many emails per day does a mental practitioner receive per day?
I do not find an estimate. There are anecdotal accounts, such as here and here; here answers go from 50 to 200 emails per day.
There is a nice APA report from 2015, but it does not discuss this aspect.
I am looking at the general population of workers as well, although this approach implies an increase in the variance, and thus in the uncertainty on whether the answer I could get is similar to the answer I would get from practitioners; here it seems that office workers receive 40 email per day.
My curiosity started after I read some articles (e.g. this one) on ethical concerns about emails, so I started to wonder how much a mental practitioner might spend per day reading emails.

I am not a psychologist or neuroscientist, but I reading on this topic for some research on time consumption in the occupation.

Any insight or reading reference would be very welcomed!