The term "junk mail" is problematic. It is a derogatory term that fails to specify exactly what it belittles. Sure, take-away leaflets are clearly junk mail. But what about a personally addressed advert from a company you recently bought something from? What about a free newspaper stuffed full of advertorials and inserts? What about paper directories?

To have a meaningful discussion about "junk mail" we need to know what we are talking about. That is surprisingly difficult in the UK. The junk mail industry's lobby group, the Data & Marketing Association (formerly known as the Direct Marketing Association), doesn't provide any definitions in its Code of Practice. They seem to think that any advertisement pushed through the door is "direct marketing". Such a broad definition is unhelpful. It is daft to throw a catalogue someone has requested and an unsolicited take-away leaflet on the same heap.

For this guide I use the following definitions:

Advertising mail

Any advertising material that is distributed through the letter box. The items may be addressed or unaddressed and may include items such as free newspapers, political propaganda and phone books.

Addressed advertising mail

Any advertising material that is distributed through the letterbox and includes an address (or delivery point, in Royal Mail jargon). The DMA's preferred weasel word ("direct mail") can be used instead to describe this type of advertising mail.

Unaddressed advertising mail

Any door-to-door advertising material distributed through the letterbox. Such items never include an address and the term "direct mail" should be avoided for such literature.

Junk mail

A derogatory term for any type of unwanted advertising mail.

Other classifications

We can also make a distinction between solicited or unsolicited advertising mail. Historically, the junk mail industry adopted a rather liberal interpretation of "solicited". Marketing professionals used to spent a great deal of time thinking of better ways to hide opt-out boxes when requesting personal data, as anyone who failed to tick the opt-out box had automatically given consent for their personal data to be used for "direct marketing" purposes. Typically, that "consent" included selling personal data to "carefully selected" third parties as well. Thankfully, such practices have been mostly banned by the GDPR. Consent nowadays has to be "informed". In any case, I use a more narrow definition:

Solicited mail

Any addressed advertising mail for which active consent has been given (i.e. the recipient of the advertisement has actively and knowingly agreed to receive advertisements from the sender). In terms of the GDPR, this type of ads use the consent basis.

Unsolicited mail

Any addressed advertising mail for which no active consent has been given.