The twitter group PunishmentPosse appears to have released 28882 E-mails from Clinton's private server, available from Archive.org as either a torrent or direct link.
The files appear to be 28882 PDF files, each of which appears to be state department E-mails to Hillary from 2012 to 2016. Some E-mail addresses have been redacted, and occasionally an entire page has been blanked out. Everything seems legitimate at first glance and to my untrained eye.
Note that this is not a wikileaks drop, and the data might not be authentic.
KimDotcom has previously hinted that Clinton's E-mails might be released on Hillary's birthday (October 26th). He has not claimed responsibility, but has recently made a few cryptic tweets today.
(Kim Dotcom may have an axe to grind, because Hillary Clinton signed his US extradition order)