How Can Direct Marketing Lead to Spam Complaints?

Direct marketing can add an email collected for an order receipt to a coupon list without an opt-in, leading the buyer to mark the messages as spam.
Repeated reports can cause email providers to place later campaign messages in spam folders, even when other customers asked to receive them.
Customers usually give their email at checkout to receive a receipt, order confirmation, and shipping updates.
The business may copy that address into its marketing list without asking for separate permission.
Coupon codes and sales messages then begin arriving after the purchase.
The buyer gave the address only for order updates, so the promotional emails may be marked as spam.
Each spam report is recorded against the address or domain that sent the email.
As the complaint rate rises, the sender’s reputation falls and filtering becomes stricter.
More campaign emails may then go to spam, including messages sent to willing subscribers.