An anonymous remailer is a server that receives messages with embedded instructions on where to send them next, and that forwards them without revealing where they originally came from.
Remailing as discussed in this article applies to e-mails intended for particular recipients, not the general public.
[1] It must be understood that every data packet traveling on the Internet contains the node addresses (as raw IP bit strings) of both the sending and intended recipient nodes, and so no data packet can ever actually be anonymous at this level [citation needed].
In addition, all standards-based e-mail messages contain defined fields in their headers in which the source and transmitting entities (and Internet nodes as well) are required to be included.
When receiving traffic addressed to this user, the server software consults that list, and forwards the mail to the original sender, thus permitting anonymous—though traceable with access to the list—two-way communication.
[citation needed] More recent remailer designs use cryptography in an attempt to provide more or less the same service, but without so much risk of loss of user confidentiality.
If users accept the loss of two-way interaction, identity anonymity can be made more secure.
By not keeping any list of users and corresponding anonymizing labels for them, a remailer can ensure that any message that has been forwarded leaves no internal information behind that can later be used to break identity confidentiality.
Some of the aforementioned web services log the users IP addresses to ensure they do not break the law; others offer superior anonymity with attachment functionality by choosing to trust that the users will not breach the websites terms of service (ToS).
[6] Until technical changes were made in the remailers concerned in the mid-2000s, some re-mailers (notably nym.alias.net based systems) were seemingly willing to use any genuine (and thus valid) but otherwise forged address.
This loophole allowed trolls to mis-attribute controversial claims or statements with the aim of causing offence, upset or harassment to the genuine holder(s) of the address(es) forged.
In 2014, dizum.com (a Netherlands-based remailer) was seemingly blocked by authorities in Pakistan,[citation needed] because comments an (anonymous) user of that service had made concerning key figures in Islam.