ActiveSync Login Failure

I've had no problems logging into my Zoho account on my smartphone and suddenly my phone is sending a login failure notification every 10-20 seconds. I've had to put my phone on silent to stop this, risking missing calls and more importantly, not receiving emails-- which is why I have the service in the first place. I have changed nothing on my end, so I have no idea what the problem is, but I need it resolved immediately.