Final answer:
The guideline not included in Canada's anti-spam legislation is the mandatory use of electronic signatures; CASL focuses on consent, sender identification, and unsubscribe mechanisms.
Step-by-step explanation:
The question asks which guideline is NOT included in Canada's anti-spam legislation (CASL). The correct answer is D) Mandatory use of electronic signatures. CASL regulations include requiring consent for sending commercial electronic messages (CEMs), providing identification information of the entity sending the message, and having a clear means for recipients to unsubscribe from receiving future messages. However, CASL does not mandate the use of electronic signatures for these communications.