Am I able to make a e-mail list form where the enter data automatically gets put into the outgoing e

I am not certain if I am phrasing this right. But I need to include an input area on my site to join a mailing list. I'd imagine the e-mail they input might then instantly get put into an outgoing e-mail list. I have already been using CGI and formmail to receive info for example details or bills to my e-mail. Today I had want to understand the way and if the subscriber list is potential. Can anyone assist or point me to a site that will have that information? Thanks very much!!