The "soft opt-in" is an exception to the consent requirement for electronic direct marketing, as established by the ePrivacy Directive (2002/58/EC). A key condition for this rule to apply is that the recipient's contact details must have been obtained directly by the sender "in the context of the sale of a product or a service." An inquiry about purchasing a product or service establishes this pre-existing commercial relationship or negotiation. This circumstance, combined with the requirements to market only similar products and to offer a clear opt-out mechanism, allows for the application of the soft opt-in rule.

A: The rule is an exception that applies in the absence of consent, but this is not the specific circumstance that triggers its applicability. C: The soft opt-in requires a direct relationship with the individual; it cannot be used for contact details from third-party lists. D: Providing an unsubscribe option is a mandatory condition for using the soft opt-in, not the initial circumstance that permits its use.

1. Directive 2002/58/EC of the European Parliament and of the Council of 12 July 2002 concerning the processing of personal data and the protection of privacy in the electronic communications sector (ePrivacy Directive).

Reference: Article 13, Paragraph 2. This paragraph explicitly states the rule applies where a person "obtains from its customers their electronic contact details... in the context of the sale of a product or a service..." This is the legal basis for the soft opt-in.

2. Article 29 Data Protection Working Party, "Opinion 5/2004 on unsolicited communications for direct marketing purposes under Article 13 of Directive 2002/58/EC," WP90, 27 February 2004.

Reference: Section III.2.b, page 13. The opinion clarifies that the phrase "in the context of the sale" can include pre-contractual stages, such as when a customer requests information or a quote, which aligns with an "inquiry about buying a product."

3. Kuner, C., Bygrave, L. A., & Docksey, C. (2020). The EU General Data Protection Regulation (GDPR): A Commentary. Oxford University Press.

Reference: Chapter on Article 21 (Right to object), commentary on the relationship with the ePrivacy Directive. The text explains that the soft opt-in under the ePrivacy Directive is a specific lex specialis rule that requires an existing customer relationship, which begins when details are collected during a sale or sales negotiation.