In some cases, graymail can account for up to 82 percent of the average user's email inbox.
[1] Graymail was described in 2007[2] and 2008[3] by researchers at Microsoft Research looking to improve spam filtering as “messages that could reasonably be considered either spam or good (by different email users)” hence the name “graymail” was chosen to signify the subjective nature of the classification.
A 2008 paper presented at the Fifth annual Conference on Email and Anti-Spam (CEAS) describes graymail as "messages (such as email newsletters) that some users value and others prefer to block".
[4] In 2011 a report by The Radicati Group referred to graymail as "newsletters or notifications that a user may have signed up for at one time but no longer wants to receive".
Shopping deals are a good example: they’re only valid for a fixed number of hours or days but are frequently not read or opened by the recipient until after the offer has expired.