Whenever I use PHP to send emails to members of my site, the email ends up in the spam folder for most email providers like Gmail and Hotmail.
When I check the original
Its gonna be difficult to answer this without the real info (involved IPs, domainname, sender adress, full spf record etc). It also looks like this message wasn't sent to gmail directly, but retrieved from your server via Gmail Fetch (Header X-Gmail-Fetch-Info ), which makes the analysis even more complicated.
here are a few possibilities: