I also noticed that any user or guest using the contact form, the email I get as forum admin shows the sender as my own forum email address, not the email address of the guest or user like it did with 2.4.8.

So I now have a load of emails and I don't know who has sent them to me because all the senders is my email address.

Maybe time to revert back.

When you get a mail that appears to be from yourself, click on the mailheader.
In the "Reply-to" field you will see the senders mailaddress.
Tested in Gmail.

/Tommy

Thank you Tommy I realised this later on. I use the mail app in Windows 8.1 and to see who sent the email from my forum to me (even though it's an email I will not be replying to) I have to click the reply button, look at the sender's email address then I have to delete the draft reply email which seems a weird way of finding out the sender.