Apart from causing annoyance to recipients, unsolicited emails can also be deceptive and deliberately fraudulent in nature, leading to infection by viruses, identity theft, or even financial loss if instructions described in the messages are followed. Such fraudulent messages are called "scam emails".

Online scams can encompass a wide range of activities. Examples are on-line shopping scams, on-line investment scams, and "Nigerian Letters". The Hong Kong Police Force has posted specific information on "Nigerian Letters" on their website, together with some advice for avoiding the traps set by these fraudulent emails.