Off-site promotion itself is not against the law, but the key is whether the method and content of the promotion comply with Amazon's regulations. Amazon has a strict set of regulations designed to ensure fair competition and protect consumer rights. If the off-site promotion involves false propaganda, misleading consumers, or violating copyright or trademark laws, then such promotion is against the law.

For example, if the off-site promotion uses false information to attract consumers to buy, or violates Amazon's regulations on promotional activities, then such behavior may be considered a violation. In addition, if the off-site promotion involves the unauthorized use of Amazon brands or trademarks, it may also constitute infringement.

Therefore, the key to increasing Amazon sales through off-site promotion is to ensure that all activities comply with Amazon's regulations and laws and regulations, while ensuring the authenticity and legality of the information.