We are often asked by users if there is a way to tell when the recipient of a message has opened or read the message. There isn't any way for EarthLink to know if a remote recipient has read your message, but there are third-party applications you can install on your own computer that work with some popular email applications like Outlook. These will not work with Web Mail, and I'm not recommending any of them here, only mentioning that they exist. You can find them on Google.
These applications work by embedding some HTML code in the outgoing message so that when viewed by the recipient, it will send a ping back to the application on your computer and tell you when the message was opened. The reliability isn't 100%, as the recipient could be using a plain-text email reader that doesn't activate the embedded HTML, or various security tools on their own computer that will block this mechanism without the user even knowing it was there in the first place. It can also be blocked by your own security software or firewall on your end.
The concept of "read confirmations" or "read receipts" originated in the old days with closed email systems that hosted both the sender and recipient (like pre-Internet online services), so the system could "know" when the recipient opened the message. This isn't possible with messages sent over the Internet except by using software like that described above. There isn't any accepted standard for mail transport systems to support such a feature between remote systems, and privacy concerns would mandate that any such mechanism be voluntary for the recipient.
Some email applications (including Outlook) give you the option to request a receipt confirmation when you send a message, but these require the recipient to be using email software that supports this feature, and the recipient must also approve the confirmation to be sent back to you. This is basically just a reply from the recipient telling you they got the message, it isn't automatic. For techies, Outlook and some other applications implement the Disposition-Notification-To header suggested in RFC 2298. This is not generally supported by Internet mail systems, only by particular end-user applications.
So the short answer is that EarthLink can't tell when a message has been read (and neither can any other ISP), and any other method is only totally reliable with cooperation between the sender and recipient. Asking for a good old-fashioned Reply is the only surefire way to know your message has been read.