I usually check my email in the evening before going to bed and then again first thing in the morning. This means that there is a sleep-gap of 8 to 10 hours and in the morning I see the largest number of spam emails in the spam folder.
I am a big fan of Google's GMail. It does a fantastic job of correctly filtering spam into the spam folder and so it rarely bothers me and I just see a figure which tells me how many spam mails were filtered.
On any morning this number is usually between 25 and 100 so this morning it surprised me to see 568 spam emails sitting there. A quick calculation shows me that I am receiving, on average, more than 1 spam email per minute.