MsgPix is a free iPhone app that will easily show the images sent in a "legacy" SMS/MMS message, without having to separately copy and paste the link, login and password.
A legacy message looks something like this:
I've sent you an Orange Photo/Video Message. Go to http://www.orange.co.uk/mms/ Your ID is: xxxxxxx Your password is: xxxxx valid for 21 days
To view the image you would usually visit the link, then awkwardly go back and forth, coping and pasting the login and password into the web page. This app makes it much easier - one easy copy and it automatically takes you to the web site and fills in the form and displays the picture - no hassle and just a couple of touches!
(This app does not retain any data.)