From the journal Computers in Human Behavior:
Using email is one of the most common online activities in the world today. Yet, very little experimental research has examined the effect of email on well-being. Utilizing a within-subjects design, we investigated how the frequency of checking email affects well-being over a period of two weeks. During one week, 124 adults were randomly assigned to limit checking their email to three times a day; during the other week, participants could check their email an unlimited number of times per day. We found that during the limited email use week, participants experienced significantly lower daily stress than during the unlimited email use week. Lower stress, in turn, predicted higher well-being on a diverse range of well-being outcomes. These findings highlight the benefits of checking email less frequently for reducing psychological stress.
peakmemory 
Email has become such a chore. I’ve decided to check (and respond) just once a day at 5pm
What you need is a separate junk e-mail account that for use with companies that you know will send you a ton of junk e-mail. Check that once a week.
I find that the filters in the Thunderbird email client very helpful