Some people ignore the very existence of their spam folder; others, though, have a check-through every now and again to see if they've missed anything vital.
And occasionally it's hard to understand why one piece of marketing bumph has made it through to the inbox, while another is consigned to spam purgatory.
Now, though, Google has introduced a feature telling users the reasons for its decisions.
"Many of our users say the accuracy of our spam filter is one of the key reasons they love Gmail. And while we think you should never have to look in your spam folder, we know some of you may want to know why the messages there were marked as spam," says software engineer Ela Czajka.
"So starting today, we’ll be showing a brief explanation at the top of each of your spam messages. Simply look at any message in your spam folder and now you can find out why it was put there and learn about any potentially harmful content within the message."
The main reasons, according to the company, are phishing scams and similarityy to known suspicious messages - as well as user actions. So if you've marked previous missives from your ex-girlfriend as spam, don't expect to see the new one where she tells you she's made a big mistake.