So are you logging into your earthlink account using the browser? Or are you actually getting the emails forwarded from earthlink to your device? Also I think that earthlink only offers POP3 mail, which I think can only be refreshed at max every five minutes. My thought is that earthlink mail is removing the links, just a hunch. Send yourself an e-mail with a link of any website (copy from address bar on your pc)and see if it works on your device to test it.
To solve the problem I would consider getting access to a Hosted Exchange Server. It is designed for Outlook and it will sync up everything in Outlook to your device seamlessly. I use
www.1and1.com for $7/month. There are several other companies as well, I think HP has one for $3/mo. Its hard to explain in writing. If you need a hand send me an e-mail aaron@ntreo.com.