I subscribe to a news outlet that sends SMS messages to my Galaxy S5. The funny thing is that I cant set a custom notification tone for this sender using Handcent or the Default SMS App but I can set it Using Goolge Handouts. I have attempted to add the sender (and it shows up as an SMTP address) in my messaging app to the contacts list and set a custom notification tone. The fact that it only shows up as an SMTP address in Handcent is something that I think may be causing the problem but I'm not sure. However I can do it with Google handouts.