explain the laws of email marketing?

Legally, it is acceptable to purchase email lists. But here's the catch: For each email list you purchase, you must gain explicit permission from the list's subscribers before using it for any other purpose. Although recipients may have provided permission to be included on the list you purchased, they must do so again for you.

1.Make your own mailing lists rather than buying pre-made ones.

        2.Make sure your mailing lists are free of spam traps, phoney emails, and misspelt emails by using double opt-in.

       3.Get your users' express consent.