As promised, here are a few tips on how to keep your inbox clutter-free and organized.. While it may take a little time to get it all set up, in the long run you will be much more organized with much less effort.
In Outlook, as well as many online email providers like Google, there are 'Filters' or 'Rules' which will automatically categorize emails based on their sender, key words or phrases that are in the email.
So for example, you get an email from email@example.com who is from "Company X", so if you were to set up a rule, any emails coming from firstname.lastname@example.org would be assigned a label or labels (Gmail) or moved to a specific folder (Outlook) that corresponds to Company X.
The process is simple, so let's start with Outlook. The easiest way to get this done is to create the rules as the need arises, so you get an email from email@example.com and you want to create a rule that automatically moves it into a folder. Right click on the email and select Rules -> Create Rule. As pictured below (click for larger version):
This will open the following window:
You will want to select the options you want, and then select "Move the item to folder:". This will allow you to select the folder you want to move the email to, or create a new folder to move the email to. Now every email that comes from, or contains words in the email or subject will be moved to the specified folder.
But wait, it won't be in the Inbox! That's easily remedied by creating a "Search Folder" which will show all of your Unread Messages--regardless of which folder they are in.
If you don't already have an Unread Mail search folder, simply right-click on your Search Folders (bottom of folder view) and select "New Search Folder..."
Select Unread mail and click OK:
And now you can view all unread mail, regardless of the folder it's in.
Next we will take a look at Gmail, another popular email service.
Much like Outlook we will start with an email we have already received, select it in your inbox and click More -> Filter messages like these:
This will bring up the following window which will allow to add more options to the filter.
Next click on "Create filter with this search>>" which will bring up the following window where you will want to select "Apply the label:..."
Select the label you want to automatically apply, and you're done! Now this label will automatically be applied to the emails as soon as they arrive in your inbox. In order to remove them from your inbox and move them to the label, just "Archive" the message.
One of the nice things about labels is that you can have more than one per email, so if more than one person is involved in the email conversation you don't have to decide which folder to put it in, you can assign multiple labels, all while keeping it in the inbox if need be.