This is for anyone still having still this problem with Scannable email using wrong default 'from' address - go to iPhone settings> Mail> (Step 1) Accounts> (check the correct email you wish to use is listed here) add the email you wish to use. (Step 2) go back to 'Mail' and scroll down to the bottom and 'Default Account' - select the correct email you wish to use - Scannable will use this in the 'From'.