Outlook cannot connect to your SMTP server

Outlook cannot connect to your SMTP server

Cannot send emails through Outlook anymore. Settings haven't changed. I can receive but not send. 

smtp.zoho.com
Port: 465

Email was working fine with Outlook 2013 on Friday morning, but started giving me send/receive errors in the afternoon. 

I can send emails through the Zoho web-mail page, so why is it suddenly failing in Outlook? Need a fix for this ASAP!