What content is prohibited by email laws (false headers, deceptive subject lines)?

Email laws like CAN-SPAM (US), CASL (Canada), and GDPR (EU) prohibit specific content practices. False or misleading header information is universally banned: the \"From,\" \"To,\" and \"Reply-To\" fields must accurately identify the sender and not impersonate others. You cannot forge headers to make emails appear to come from someone else or disguise your identity.

Deceptive subject lines are prohibited when they misrepresent the email's content or purpose. CAN-SPAM specifically requires that subject lines not be \"likely to mislead a recipient\" about the message contents. \"RE: Your Recent Order\" when there was no previous conversation, or \"Urgent: Account Problem\" for promotional content, violates this standard. The subject must give recipients an accurate expectation of what they'll find inside.

Additional content requirements include: clear identification as advertising (if applicable), valid physical postal address, visible unsubscribe mechanism, and honoring opt-outs within required timeframes. The penalties are substantial-CAN-SPAM violations can cost up to $50,120 per email. These aren't just legal technicalities; they're baseline standards for honest communication. Violating them damages both legal standing and brand trust.