Answer: optsin

AnswerCrossword Clue
OPTSINDecides to participate
OPTSINDecides to join
OPTSINChooses to participate
OPTSINChooses to get e-mail, maybe
OPTSINChooses to take part
OPTSINDoesn't decline
OPTSINChooses to join
OPTSINAgrees to participate