It’s no secret that I run very little in the way of spam filters, and what filters I do run don’t throw away mail, they just shove it into various mailboxes.
Looking at my mailboxes currently I have 11216 unread messages in my mail.app junk folder, 10600 unread messages in my work spam assassin folder and 29401 messages in my personal spam assassin folder (mail getting more than +7 on our version of spam assassin gets filtered into these folders). I went through and marked all of my messages read back in mid-January. That’s a little over 50,000 messages in a little over 5 months or slightly more than 2700 spams a week.
But these are messages I don’t have to deal with so while they’re somewhat annoying and a bit of “wow, my addresses are everywhere” they’re not a huge deal. I have strong enough filters for wanted mail that I can special case it.
Spam in a mailbox makes it harder to find wanted mail.
I use tagged addresses whenever I sign up for something. This means I can identify and separate senders I gave addresses to from those senders who are spamming me. I can trivially filter out solicited from unsolicited email. In the same amount of time that I received 50,000+ spam, I received just over 8000 real messages. If I didn’t have an easy way to sort out spam from mail I signed up for, I’d have to manually delete 6 messages to find one message I wanted.
I don’t know how much experience you have with manually deleting spam, but I do it daily (my filters aren’t 100%) and I spam a message I shouldn’t have at least once a month.
What happens when spam and real mail mix together?
I have another mailbox, that belongs to my second non-work/school related email account. I acquired this address back in 1993 and have kept it for those 20 years. This mailbox is behind a commercial filter, but as this address was on the internet long before commercial mail or spam was a reality, it still gets a lot of spam. This mailbox is also associated with a couple discussion lists, ones I follow but don’t post on very often.
Last year I started a project to look at what happens when you unsubscribe from spam. I unsubscribed from every message coming into this mailbox for a month. Then I recorded every message that came into this mailbox for 2 months. My goal was to then count the number of messages coming into this mailbox for the next 6 months, to see what the long term consequence of unsubscribing from spam.
Because I am counting spam, I’m leaving all the spam in that mailbox as unread mail until it’s recorded. Right now there are 2709 unread messages in that mailbox. The problem is, some of that mail is actually discussion mail. But in order to find it, I have to rely on searches to find the list mail. It means I’m a lot less likely to actually look in the mailbox to find the mail I want, it’s just too painful and annoying to do it, and I don’t care that much about the discussions. If I had to do this with all my discussion lists, I’d probably declare mailbox bankruptcy and find myself a new email address. It’s that annoying.
Spam filters are a net benefit.
My point is that filters make and keep email useable. Unfiltered mailboxes quickly fill up with unsolicited mail that overwhelms any commercial or personal usage.