Carrier,
The problem with free email like everyone.net is that spammers get a hold of email accounts and use them to send out their spam. As ISPs start taking a more active roll in blocking Spammers, more and more IP Addresses will end up blocked. Those blocked IP Addresses will be Mail Server IPs.
Until spam is under control and spammers are behind bars, only expect it to get worse.
Take Care,
Richard