Problems logging in to two separate email clients (Outlook and iPhone)

Problems logging in to two separate email clients (Outlook and iPhone)

I have used Outlook and iPhone as my ZoHo email clients for several years now with rarely an issue...yesterday afternoon both clients started asking me for a password (which was NOT changed) to access my accounts.  What is the problem. This is clearly a ZoHo issue and not a mail client issue since both clients started having problems at the same time.  BTW, I can access my mail through the ZoHo web site just fine.  Someone PLEASE HELP!!!