Greylisting

Greylisting is a method of defending e-mail users against spam. A mail transfer agent (MTA) using greylisting will `temporarily reject` any email from a sender it does not recognize. If the mail is legitimate the originating server will, after a delay, try again and, if sufficient time has elapsed, the email will be accepted. ==How it works== A .....
Found on http://en.wikipedia.org/wiki/Greylisting

Greylisting

Process of routing email to a bulk folder if it is borderline spam, as determined by a receiving ISP
Found on http://www.superglossary.com/Glossary/Technology/Email/
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