Spam (or Junk)
Spam, also known as junk mail, refers to unsolicited and often irrelevant or inappropriate email messages sent in bulk to a large number of recipients.
Spam, or junk mail, is unsolicited bulk email sent to people who did not ask for it. Much of it is commercial, and a lot of it is fraudulent or deceptive.
The line between spam and legitimate marketing is consent and honesty. Marketing email goes to people who chose to receive it, says who sent it, and offers a working opt-out. Spam does none of that and often disguises its sender or subject to get past filters.
What the law says
In the US, the CAN-SPAM Act does not apply only to bulk mail. It covers any email whose primary purpose is commercial promotion, including business-to-business email, and requires accurate headers, a truthful subject line, identification as an ad, a valid physical postal address, and an opt-out honored within 10 business days. Source: the FTC’s CAN-SPAM compliance guide.
In Canada, CASL generally requires consent, sender identification, and an unsubscribe mechanism for commercial electronic messages, with limited exemptions. Source: the CRTC’s CASL guidance.
Why it matters
Once recipients start marking your mail as spam, mailbox providers have direct evidence that people do not want it. A reputation built that way is slow to repair, and legitimate campaigns sent from the same domain can be filtered along with the rest.
How spam filters work
Filters generally combine several inputs: the content and links in the message, the reputation of the sending domain and IP, authentication results, and how recipients react after delivery. No single signal decides whether a message lands in the inbox, a promotions tab, or the spam folder.
Common mistakes
Buying or scraping a list. Hiding the unsubscribe link. Sending a marketing message with a subject line that pretends to be a receipt or account notice. Each of these makes the mail look like spam to filters and to the people receiving it, whatever the sender intended.
To keep messages out of the spam folder, read why emails go to spam.