Incoming text message auto filled the "TO" field? I received an MMS messages this afternoon on my iPhone 6.  When I opened it, it was clearly a spam text message.

I did not recognize the sender.

I went to the link in the email on a spun up virtual machine and it just went to some Gwen Stefani article.

However, what caught my eye was that the "to" field had several old gmail contacts who I haven't reached out to in some time. (screen shots below) There are 9 email addresses in the "to" field. 

Is it possible for someone to compose a text message which then fills in the TO field automatically? I checked with people in the "TO" field and they didn't receive this message.
This spammer must have acquired these contact numbers from an email account's contacts page belonging to one of the people who received this. Then, they sent a text message to some of the contacts they found. The To field is auto-filled by your phone with all the people who received the text. For instance, if I texted a message to you and some guy (let's call him Joe Smith) the To field would be filled with "To John Ramos and Joe Smith", indicating that any text you send in that group chat will go to the people in said group chat; that's exactly what's going on here.