I got a message from my bf on my iphone and could reply as normal, but when I sent a picture, a new thread was added in my inbox. The same thing happened when I deleted both of the threads and wrote a new message. The one I sent was there and when he replied, another thread was suddenly in the inbox. Why does this happen?
When you open your Pictures app, select the picture you would like to send, and then select send in an email, it doesn't know that it "should" be part of the previous thread. It is a new email. If it was added to the thread, then technically, any email that you send to him should part of the same thread. Unfortunately, even if you type the same Subject in as the thread, it will still not show in that thread.