Editing Open mail relay (section)

== Anti-spam efforts ==
Many Internet service providers use [[DNSBL|Domain Name System-based Blackhole Lists]] (DNSBL) to disallow mail from open relays. Once a mail server is detected or reported that allows third parties to send mail through them, they will be added to one or more such lists, and other e-mail servers using those lists will reject any mail coming from those sites. The relay need not actually be used for sending spam to be blacklisted; instead, it may be blacklisted after a simple test that just confirms open access.<ref>{{Cite web|url=http://www.dotcomeon.com/|title=Big brother network now controls your E-mail}}</ref>{{Better source|reason=Questionable source|date=October 2013}}

This trend reduced the percentage of mail senders that were open relays from over 90% down to well under 1% over several years.<ref name="IMCR-016">{{Cite web|url=http://www.imc.org/ube-relay.html |title=Allowing Relaying in SMTP: A Series of Surveys |access-date=2008-04-13 |last=Hoffman |first=Paul |date=2002-08-20 |work=IMC Reports |publisher=[[Internet Mail Consortium]] |archive-url=https://web.archive.org/web/20070118121843/http://www.imc.org/ube-relay.html |archive-date=2007-01-18}}</ref> This led spammers to adopt other techniques, such as the use of [[botnet]]s of [[Zombie (computing)|zombie computers]] to send spam.

One consequence of the new unacceptability of open relays was an inconvenience for some end users and certain [[Internet service provider]]s. To allow customers to use their e-mail addresses at Internet locations other than the company's systems (such as at school or work), many mail sites explicitly allowed open relaying so that customers could send e-mail via the ISP from any location.<ref>{{Cite web |url=http://preview.samspade.in/d/nanaefaq.html |title=news.admin.net-abuse.email FAQ |access-date=2008-04-08 |last=Atkins |first=Steve |url-status=dead |archive-url=https://web.archive.org/web/20120727212031/http://preview.samspade.in/d/nanaefaq.html |archive-date=2012-07-27 }}</ref> Once open relay became unacceptable because of abuse (and unusable because of blocking of open relays), ISPs and other sites had to adopt new protocols to allow remote users to send mail. These include [[smart host]]s, [[SMTP Authentication|SMTP-AUTH]], [[POP before SMTP]], and the use of [[virtual private network]]s (VPNs). The [[Internet Engineering Task Force]] (IETF) has written a [[best current practice]]s covering Email Submission Operations in RFC 5068.

Note that the above only becomes an issue if the user wishes to (or has to) continue to send e-mail remotely, using the ''same'' SMTP server which they were previously accessing locally. If they have valid access to some ''other'' SMTP server from their new, remote location, then they will typically be able to use that new server to send e-mails as if from their old address, even when this server is properly secured. (Although this may involve some reconfiguration of the user's [[email client]] which may not be entirely straightforward.)

The [[CAN-SPAM Act of 2003]] makes it illegal to send spam through an open relay in the [[United States]], but makes no provision on their use for personal e-mail or their operation in general; the effectiveness of the act has been questioned.<ref>[http://www.mondaq.com/article.asp?article_id=28901 United States: A New Weapon in The Fight Against Spam]</ref><ref>[http://www.pcworld.com/article/id,114287-page,1/article.html Is the CAN-SPAM Law Working?]</ref>