If Gmail’s spam and newsletter filters are letting too much slip through, or if you use a private email service with a bad spam filter, then try this solution: quarantine all email until the sender has confirmed that they’re not spam. This is your homemade spam filter.
Blogger Beetle B. set up their email server to automatically reply to every email from a new sender. The reply includes a link, and the link goes to a site where the sender has to enter their email address to confirm that they’re not a spammer.
It’s a bit of a pain for the sender, but not a huge pain, so it hasn’t stopped Beetle B. from getting any important emails. They’ve used the system for over a year, and so far it works well enough for them to recommend it to anyone frustrated over spam and low-priority email. In a follow up, they list several services that will help you create your own auto-reply without a ton of work.
If a sender doesn’t fill out the form, their email gets sent to a quarantine folder, much like a typical spam filter. Beetle B. checks theirs daily, and still finds it far better than the old way—where they’d get buried in unimportant email and fail to answer important ones for months.
If you’re worried about important emails not getting through, you can mitigate that with a whitelist. When Beetle B. started their system, first they whitelisted everyone they’d emailed with. You can set your own criterion for whitelisting. Beetle B. made their whitelist quite large, which initially let in some unwanted newsletters, but they just took those newsletters off the whitelist as they came in.