(a) A person may not intentionally take an action to transmit an unsolicited commercial electronic mail message unless:
(1) "ADV:" appears first in the subject line of the message or, if the message contains obscene material or material depicting sexual conduct, "ADV: ADULT ADVERTISEMENT" appears first in the subject line; and
(2) the sender or a person acting on behalf of the sender provides a functioning return electronic mail address to which a recipient of the message may, at no cost to the recipient, send a reply requesting the removal of the recipient's electronic mail address from the sender's electronic mail list.
(b) A sender shall remove a person's electronic mail address from the sender's electronic mail list not later than the third day after the date the sender receives a request for removal of that address under Subsection (a)(2).