10 Essential Gmail Hacks and Add-ons!
Click on “Outgoing Server (SMTP)” and click on the Edit button. Change the port to 587 and select TLS under “Use secure connection”.

Then click Ok and ok on the Account Settings window.
Click on the Get mail button and enter your Gmail password. Thunderbird will retrieve your e-mail and download the messages into your Inbox. Every time you re-open Thunderbird, the program will ask you for your password for security reasons. If you get tired of entering the password, put click the checkbox to have it remember the password.
Minimize Mozilla Thunderbird; we need to setup Attachment Extractor now.
Download Attachment Extractor. Save the file to your Desktop. Bring up Thunderbird, click Tools and select Add-ons. Click on the Install button. Navigate and find Attachment Extractor and open it. Now click on the Install Now button and Thunderbird will install the extension. When requested to restart Thunderbird, click on Restart Thunderbird.
When Thunderbird restarts, click on the attachment button to sort the e-mails by attachments. This will make all the e-mails with attachments go to the top.

Hold down the Ctrl key and click on all the e-mails with attachments or at least the ones you want to download. Right click on one of the messages and select Extract Attachments To. Click on Browse and create a new folder for these attachments.
The attachments will begin downloading to your computer and will give you a progress window. After they are downloaded, you will have a folder on your Desktop with all of the attachments.

Manage Multiple Gmail Accounts
Gmail Manager is a Mozilla Firefox add-on that allows you to manage multiple Gmail accounts without having to login to each of them individually. Since most of you probably have more than one Gmail account, this will be a very useful Firefox add-on.
Download Gmail Manager from Mozilla's web site. Click on the Add to Firefox button and install the add-on like any other add-on.
After Firefox restarts, click the small 'M' in the bottom, right hand corner of the screen.

Click on the Add button to add a Gmail account and type in your e-mail address and password into the dialog box.
When the program returns to the main screen, select “Automatically login to this account at startup” and click the Apply button.
If you have another Gmail account, click on the Add button again and enter the e-mail address and password for that account.
After you are done adding all of your Gmail accounts, click on the Ok button. When you open your web browser, you will notice in the bottom, right hand corner that it lists the e-mail messages present on your Gmail accounts.

To change which Gmail account is listed, right click on the e-mail and select your other account.
Share Links with GmailThis!
GmailThis! is a useful bookmarklet that allows you to quickly send an e-mail message that includes a link to a certain webpage.
To use GmailThis, click here.
Drag the GmailThis! link located just below the “Big, Important News” warning into your browsers links bar or live bookmarks area.

If you did it correctly, you should now have a new bookmark or live bookmark named GmailThis!

When you find a webpage you want to e-mail to someone click on the GmailThis! bookmarklet and log in to your Gmail account. Type in their e-mail address and click send after typing a short message explaining what the link is.
Alternatively, if you want to be lazy, you can use this bookmarklet to send someone an e-mail. Delete the link out of the body and change the subject of it. It will send just like any other e-mail.
Use Gmail while Offline
If you have ever feared not having Internet access and not being able to access that one important e-mail, this one is for you!
To enable this feature, you need to login to Gmail and click on the Settings button in the top right corner of the screen. Now click on the Labs tab.
Locate the Offline lab feature. Click on Enable and select Save Changes.

The page will refresh and go back to your Inbox. In the top right corner of the screen, you will now have a new option named “Offline”.
When you are ready to download the messages to your computer, click on the Offline button. When the pop-up comes up explaining what Offline Gmail is, click on the Install button. It will open a new window to the Gears web page. This is a required download, so you have to download it. Gears is the application that lets you store your e-mail on your local computer.

When Gears is done installing, you will have to restart the web browser, click on "Restart Browsers Now" when you are ready.
When you re-open Gmail, you will get a security warning stating that Gmail is trying to use Gears. Put a checkmark in the box next to that states “I trust this site. Allow it to use Gears” and click on the Allow button. It will also ask if you want to create a shortcut on your Desktop, Start Menu and Quick Launch bar. We recommend you create one of these shortcuts, put a checkmark in the appropriate boxes.
Gmail will start synchronizing your e-mail to your computer, please be patient.

When you are offline, just click on the appropriate shortcut and Gmail will open up with all of your e-mail since your last synchronization. Gmail will automatically synchronize when you login to Gmail on this computer, so no need to worry about manually synchronizing.