I always found it easier to add a shortcut so that it shows in the 'Other Mail' dropdown located under your folder list. This way the link is available in iNotes as well as Notes.
Click 'More -> Preferences'
When the Preferences dialog opens, click the 'Access & Delegation' tab, then the 'Shortcuts to Others' mail' tab.
Click the dropdown next to 'Create Shortcuts to open the mail files of these people', and add the names of your shared mail accounts there.
Click OK.
Close & reopen your mailbox and you should now see the links.