A. Establish a direct Opt-in process for all leads
B. Email leads who have been inactive for more than 6 months
C. Purge the database of inactive leads
D. Purchase lists from data vendors
Explanation:
Reference: https://nation.marketo.com/t5/Knowledgebase/What-is-a-spamtrap-and-why-do-they-matter/ta-p/248282