@article{oai:yamagata.repo.nii.ac.jp:00000922,
 author = {山本,  広志},
 journal = {山形大学紀要. 工学 = Bulletin of Yamagata University. Engineering},
 month = {Feb},
 note = {論文(Article), In an attempt to investigate the features of spam emails from the viewpoint of MTA, experiments were\nmade in 2009 with five real servers installed in Japan and a domain name under .jp. It has been found that\nnot only did a group of spam emails arrive at the server with a high MX priority in the DNS, but also\nanother did at the one with a low MX priority in comparable numbers and the remaining mails at the other\nwith A record in one fewer number of digits. 99.99% of these spam emails came via IPv4 whereas only\n0.01% via IPv6. The countries of origin where their IP addresses were assigned to most were Brazil, Korea,\nVietnam, China and India in descending order. These five countries made up 42 % of all. 19% of envelope\nfrom domains in the spam emails were identified as the destination domain. 51% of them had their existent\ndomains, but were not reachable email addresses. Reachable addresses were 27% of all. Although SPF and\nSender ID were registered in 31% and 35% of domains respectively, DomainKeys and DKIM were less than\n0.05%. In one of the experiments in which greet pause was set, about 50% connections were disconnected\nwithin 10 seconds. After that, the frequency of accumulated disconnections increased in a stair-step fashion\nuntil almost all were eventually disconnected within 120 seconds.},
 pages = {27--36},
 title = {MTAから見たSPAMメールの特徴},
 volume = {32},
 year = {2010}
}