If you want to access your email messages quickly without having to login over and over again, then an email client like Thunderbird is very helpful. But if you do not want to use a dedicated email client software, then the best option is AOL Mail Preview extension for Firefox. This new extension from AOL allows you to quickly access your AOL Mail, Yahoo! Mail and GMail inboxes right from the Firefox toolbar. This way you can read the latest email messages right from the toolbar as well as compose new email messages if required.
After you have installed the AOL Mail Preview extension in Firefox, you would see a new icon in the Firefox toolbar. You can right-click on it to see popup with three different tabs for AOL Mail, Yahoo! Mail and GMail. You have to click on the Sign in button for all of these to sign in using their respective passwords.
If you do not want all of these email accounts to appear in the popup, then you can open the AOL Mail Preview settings by clicking on the gears like icon. Here you can check or uncheck the email services that you want to appear or disappear from the interface. You can also choose a default language for the interface from these settings.
When you have signed in to any of the supported email services (AOL, Yahoo! or GMail), it would populate the respective tab with the latest email messages from their inbox. You can scroll down to see older email messages. You can also compose new email message from the same interface.
Conclusion: The AOL Mail Preview extension for Firefox allows you to access your email messages from AOL, Yahoo! or GMail right from the Firefox toolbar. This way you can check for your new email messages without having to open the full fledged email websites.
You can download AOL Mail Preview extension from https://addons.mozilla.org/en-US/firefox/addon/aol-communication-suite/.