This is a two-phase system, but it's pretty easy to set up. First off you want to make friends with the plus symbol on your keyboard. You can use it to create specialized email addresses without creating a new email account. So if your email address is jimmy at iCloud dot com, you can use jimmy+shopping @ iCloud.com, jimmy+newsletters @ icloud.com, or jimmy+friendrequest @ icloud.com and all of those messages will still get delivered to you.
Using the + Sign for Email Filtering
Gmail, iCloud mail, and Outlook.com mail all offer this option, Yahoo! Mail is set up slightly differently, and you'll want to consult the help for your email provider to see how “mail tagging” or sub-addresses works for yours if it isn't listed above.
Once you start using these new addresses, then you can start filtering your messages based on them. For example, update the email address on all your social media accounts to use jimmy+friendrequest @ iCloud.com, then set up a rule that directs any mail addressed to jimmy+friendrequest @ iCloud.com to a separate folder. Then you can browse through those messages at your leisure instead of having them clutter up your inbox.
A Dedicated Mailbox
Since you can use anything at all after the plus sign, you can even narrow things down by stores you shop at regularly or any other source you want to track. A nice side effect of this is that you can see if you start getting spam at one of these addresses, which will tell you what companies are selling information or at least storing it really insecurely. Another bonus is that you can start using a different tag after the plus and ditch the other one altogether but anything addressed to your “real” address will continue to show up normally.
If you regularly receive mail from a variety of similar sources, this is an easy way to do some basic filtering and help streamline the email avalanche.