Anonymous email through chaining remailers (mixmaster, cypherpunk, nym, etc.) seems dead, perhaps killed off by spam, which is a shame because anonymous communication remains very important in society. This is an example of technology getting worse, not improving, over time. (It is possible anonymous email is actually just fine; I haven't tested or kept abreast of its deployment.)
Can it be resurrected? Hashcash and bitcoin offer spam mitigation.
There needs to be lots of mixing to preserve anonymity, but attackers can and probably have created many bad hosts.
There are two classes of recipients of anonymous email: those who wish to receive anonymous email, and those who do not. In the former, e.g., a journalist receiving a leak, anonymity needs to be preserved from both the journalist and eavesdroppers/surveillance. In the latter, people with power who would like to unmask and punish those who send unpleasant emails to them -- they have the power to punish.
That people with power wish to see anonymous email as a deployed technology go away makes one suspect malice rather than incompetence as the reason for its demise, despite the adage to the contrary. How would one purposely destroy anonymous email deployment?
Perhaps creating a throwaway Gmail account, etc., is good enough for anonymity these days. Is it? It seems vulnerable to subpoena or voluntary cooperation.
People wanting to receive anonymous email can create a website which accepts HTTP POST, which a sender can access through Tor. Are there other, better ways? What are the best practices? All newspapers should offer this, prominently.
Anonymous publishing, Tor onion sites and Freenet, seems alive (so far), and can and is being used to attack people with power. Is anonymous email for that purpose redundant?