Roughly four. The 'personal' email address (although I have some work-related emails on it) which is on Gmail, so I have push notifications on my phone. I also

Roughly four. The 'personal' email address (although I have some work-related emails on it) which is on Gmail, so I have push notifications on my phone. I also use webmail. The work address from the institution I'm currently at and the address from the one where I'm currently on leave. These I check daily (or four times a day if I'm bored) on their webmail interfaces. The old personal address (also on Gmail) which I've discontinued in 2014. This I check once a week.