It may be desirable to have mail.una.ca (Zimbra) create new windows such as when you wish to view both an email and a calendar.
Safari may block pop up windows which prevents the opening of a new window.
To allow pop ups go to the Safari Menu -> Preferences -> Websites tab.
Then in the left column labelled General -> Scroll down to Pop-up Windows.
Change mail.una.ca to -> Allow.
In Chrome you can do the following:
Chrome menu -> Preferences. Search for ‘Pop-ups’.
From sites search for mail.una.ca
Open the disclousre triangle for mail.una.ca.
For ‘Pop-ups and redirects’ use the pull down menu and choose allow.