You could collect wedding invitations the old fashioned way and make a list of all your guests, then text or call to request their address. Another option is to make an account through a website that emails or texts your guest list and asks them to respond with their address. There are quite a few free options for doing this. Also, some people simply put it out there on social media that they're getting married and would like a direct message with people's addresses if they are interested in receiving an announcement.