Anonymous, mass-mailed, unsolicited messages are an inbox blight that are difficult to escape. It's a battle as over 70% of all sent emails are spam. The final solution is to become a luddite hermit, or set up a new email account. But let's not be too hasty.

We've written before about what the US department of Justice defines as "unsolicited commercial e-mail". We've shown you how to hide and protect your email. We've talked about easy tricks to deal with spam.

Yet despite all this vigilance, you'll still find spam wiggling its persistent little head directly into your inbox and doing nothing to ease your email overload. Here are a few reasons why.

You're Clicking Unsubscribe

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Your first instinct is to click the little unsubscribe button that's hidden at the bottom of your email subscriptions and most spam messages. All it does now is inform the pesky spammer that they've found an email address that's in use. Delighted at his success, the spammer lets the rest of his spammer entourage know about you.

As NBC's Lisa Parker puts it, "…well, there goes the inbox". In that article, Parker quotes former hacker Marc Maiffret on what happens when you click to unsubscribe:

"In reality, that's usually an indicator to increase the level of things they send to you. We even see when you click unsubscribe, it'll take you to a website and the website will actually try and attack against your computer."

The moral of the story? If you don't know who sent the email, don't press unsubscribe.

Do This Instead: Hit delete or if it's definitely spam, flag it as such (Report Spam in Gmail, Spam in Yahoo), so your email client knows to filter future emails from that address.

You Replied to The Spammer

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When you reply to a spammer asking them to give you a break, you're doing two things that could slide your inbox into email hell.

First -- you're whitelisting the spammer's email. With that reply, your email provider thinks you know the sender and will have no future problem with new emails.

Second -- you just informed the spammer's system of an email address that's being used. Automatically, your spam levels will rise.

Do This Instead: Delete the email, or report it as spam. Whatever you do, don't interact with spam messages. Don't unsubscribe from them, don't click any links within them, don't open any files attached to them, and don't reply to them.

Your Friends are CCing You Into Messages

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When friends or colleagues CC you into messages, every other recipient in the group can see your address. If any of their email accounts are hacked, your email address will be found and harvested, making you more susceptible to spam.

Do This Instead: When sending email to a long list of people, enter their email addresses into the BCC field, not the CC field. Get your friends to do this too. Everyone will still receive the email, but they will not be able to see each other's email addresses.

You Didn't Read The Small Print

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Disreputable sites (or dishonest employees of those sites) that you sign up to can illegally sell your email address to other companies and spammers. Unfortunately, there's not much you can do about this, other than only sign up to sites that you trust.

More reputable sites will risk their reputation and prosecution by illegally selling your email address. But, during the sign-up process they may ask you something along the lines of,  "Tick this box if you do not want us to pass your information on to other companies who have offers that you will be interested in". In their small print they may also describe what they're allowed to do with your information, such as swapping it with other "relevant" companies or renting out their subscriber list in order to use your personal information to increase their revenue.

When Adam Tanner looked into how the American Civil Liberties Union got hold of his information, it was explained that the organization:

"...rents out the list of its own contributors to other groups for about $75 per 1,000 names. Over the course of a year such rentals bring in $100,000 in income, but it’s mostly a break-even business. The ACLU in turn spends $60 to $125 per 1,000 names to do their own fund raising. When possible, they swap lists with other organizations without charge."

Do This Instead: This kind of practice is widespread. When signing up to a website or making an online purchase, ensure the site is reputable, be sure to check the terms and conditions of the site, and always choose not to have your information shared with other third parties if given the option.

Find Out Who's Sharing Your Email Address

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If you want to keep an eye on which sites may be sharing your email address, you can use the technique called Plus Addressing, which HowToGeek explains:

Essentially, plus addressing means if your email address is DONOTSPAMME@gmail.com, then you can also receive email on DONOTSPAMME+citibank@gmail.com.

So here’s the plan. For each and every one of your online accounts [some accounts do not allow the '+' character, however], you will change your email address to DONOTSPAMME+accountname@gmail.com, where DONOTSPAMME is your actual email name, and account name is set to the account you are logging into.

Then, when you receive a spam message, you can see exactly which Plus Address the email was sent to, highlighting where the spammer found your details.

Or, consider having a separate email address for your online subscriptions and purchases. Even if you begin to receive spam, at least it won't be infiltrating your primary email account.

Unfortunately, it seems that avoiding spam completely is impossible, but by taking heed of the advice in this article and the other articles linked to, you'll stand in good stead to keep your inbox uncluttered and safer, for much longer.

What else do you do to keep you inbox clean? What is your anti-spam advice? 

Image Credits: Ab in die Tonne ... 114/365 by Dennis Skley (Flckr), Hacking by Johan V. (Flickr)