Yahoo! Inc. claims patent rights concerning DomainKeys and DKIM. Details of the claim can be found at . Their licensing statement from that page reads as follows, as of 2007-02-30: "Yahoo! licenses its Necessary Patent Claims contained in the patent(s) and patent application(s) disclosed above under either of two separate license agreements, one of which is the DomainKeys Patent License Agreement (v1.2), and the other is the GNU General Public License v2.0 (and no other version)." It is believed that this will cause normal users no legal problems, but the packager can't guarantee anything. For more information about DKIM, see http://mipassoc.org/dkim/