Knowledgebase: Proofpoint Essentials
What is the difference between Spam and Opt-in Email?
Posted by Richard Kennedy on 07/03/16 15:30


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?

Another term for spam is unsolicited commercial/bulk email. This is a
reasonable description of at least some of the e-mail that we define as spam. It may not be
apparent to the recipient how the sender got their address, and it may seem like spam.
But not all unwanted mail is spam.

Spam messages are unsolicited: that is, 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

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.

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.

Also, 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 simply by looking
at the content of a message, 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.

Some 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
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.
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