Earthlink handles mail for the earthlink.net, mindspring.com and peoplepc.com domains. They were one of the primary dialup ISPs in the early days of the Internet. They have since fallen behind other ISPs. They have partnered with a number of cable and broadband providers as well to provide email services for those customers. Earthlink does not publish either connection or sending limits.
Earthlink has a small postmaster site to help people get unblocked.
Earthlink does provide a feedback loop and early in 2013 opened the FBL to all providers, including ESPs. Signup is through email only.
Send email to email@example.com.
From Earthlink folks the email should:
The email itself should have
Earthlink does not provide a whitelist for senders.
Earthlink uses no known certification services as part of their mail delivery decisions.
Earthlink does not provide much support for senders. They do provide some information for blocked users and a way to submit IPs for blocking.
Earthlink was an early adopter of Brightmail filters. They also run an extensive internal blocklist. Their sender advice page mentions the Spamhaus blocklist, the MAPS RBL, now part of the Trendmicro email reputation services, and the CBL, as places to check if you are blocked at Earthlink, but does not go so far as to specify that they are using those lists directly.