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Proofpoint, Inc.

What is the difference between Spam and Opt-in Email?

Situation You are receiving messages you believe are spam and wondering why they were not classified as spam.
Solution See below for an explanation of what constitutes a spam message and what we consider legitimate emails.


Spam and Opt-in Email


What is the difference between Spam and Opt-in Email?


Customer-submitted messages help us to improve our spam models by providing us access to a wide variety of spam and valid mail data. Sometimes, customers are not certain whether a particular message is spam or valid mail. Also, spam messages are sometimes accidentally submitted as valid mail or vice versa. Here is a description of different types of mail and our classification of them (spam or valid).

What is spam?

Spam is unsolicited commercial/bulk email, not simply unwanted mail, even if you don't know how the sender got your address.

  • Opt In - Spam messages are unsolicited as you did not agree to receive them. If you agreed to receive a message, it is not spam. Not opting out does not constitute agreement to receive bulk commercial e-mail. In order to agree to receive bulk messages, you have to opt in. Opting in (as opposed to opting out) means that you actively agreed to receive messages.
  • Fine Print - When people sign up for an email list, there is usually legal fine print. This fine print often states that the subscriber is giving the site permission to send commercial email and/or to give the email address to the third party partners. This is the business model of those web sites - they provide a free service in return for being allowed to send advertising. The recipient might not want these mails, but if they agree to the terms of service, the mail is legitimate.
  • Commercial Spam - Some spam messages are commercial. However, not all spam messages are ads. Scams such as advance fee fraud (419) and phish messages are not strictly commercial: the sender is not trying to sell something but rather is trying to defraud the recipient.
  • Sent in Bulk - Spam messages are sent in bulk. The profile of a spam message is one or few senders, many recipients. By this definition, an unsolicited message could qualify as "not spam". For example, an unsolicited resume sent by an eager job-seeker does not qualify as spam, unless it was sent using spamming techniques (broadcast to a large number of recipients). Similarly, a grass-roots political campaign does not qualify as spam because it does not fit this profile, even if it uses a boilerplate and is mediated by a common website and mailserver.  Rather, a message like this has many senders, few recipients.
Spam Not Spam
We apply a "reasonable person" test to e-mail. Since we cannot determine the relationship between sender and recipient by message content alone, we judge whether any reasonable person would view it as spam. For the classifier, which is used by customers all over the world, we need to make sure that each message classified as spam passes this test.

Other criteria we use:
  • E-mail that includes obfuscation or chaff/hash busting text for the purpose of evading spam filters is always classified as spam.
  • Bulk commercial e-mail sent to multiple nonexistent addresses is
    always classified as spam.
Regular mail: business or personal mail that is not spam.

Opt-in (a type of valid mail): legitimate bulk e-mail that a user has agreed to receive. Typically our definition of opt-in (legitimate) mail is fairly broad because what some people might describe as
unwanted may be mail that other people want. We only block messages as spam that any reasonable person would regard as spam.

Opt-in Examples: Newsletters and Technical publications from Ziff-Davis, C|Net, etc. Online humor,entertainment, greeting card, and other personal newsletters.
Phish: a message that attempts to defraud the user by mimicking the appearance of a legitimate message from an institution (usually financial) or other authority. Valid messages from a user's bank or financial institution.
419/advance fee fraud: a spam message attempting to enlist the recipient in a fraudulent financial scam involving the claimed transfer of large sums of money. Legitimate legal documents.
Advertisements from spammers selling drugs. Legitimate correspondence from a user's physician or pharmacy.

Opt-in Examples: Online personal health and diet site mailings such as eDiets, Web MD, BabyCenter, etc.
Unsolicited advertisements for mortgages, MLM schemes, luxury items or other products. Bulk mail advertisements that the user agreed to receive: some ads can be legitimate opt-in commercial and are not spam.

Opt-in Examples: Catalog vendors such as Apple iTunes, Walmart, Dell, Macys, PC Warehouse, Harry & David, L.L. Bean, Crate and Barrel, PC Warehouse, Sharper Image, etc. These are legitimate messages that we do not want to block.
Pornographic spam or spam advertising
"adult" products.
Legitimate messages containing profanity.