I was using Gmail and needed to organize something into a category (that would show on for Configuring my Inbox) which I wanted to make specifically for it. Although I noticed that it only allows me to configure my inbox with categories such as Social, Promotions, Updates, and Forums. Does anyone know how to make a brand new category and put it as a tab on my Gmail Inbox?
One solution is to create labels, and then use multiple inboxes from the labs section of settings.
You can then have sections of your inbox that only show messages with that label.
This solution does allow you to control the logic used to assign the messages to the label. You can even manually assign messages if it is impossible to use a filter to do so.
A feature that's not everyone knows about Gmail is the subaddressing feature. It's possible to add a +TEXT at the end of your email address, like youremail+TEXT@gmail.com (where "TEXT" can be whatever you want, alphanumeric and - _ ); this feature is very powerful and can help you segment your email, especially newsletters or services (like the user in the previous answer do, using different accounts).
After you've used some subaddressed email addresses, it's simple to label it with filtering function of Gmail.
The only downside is that some sites doesn't accept email addresses with "+" character, so it's possible to use the second Gmail trick: the period. It's possible to add as many periods in the mail address (not two in sequence, and not at the end or at the beginning), so if your email i s email@example.com it's possible to even delete the period, or add another one or two, like firstname.lastname@example.org.