To setup Zoho Mail as POP account, you need to enable POP access in Zoho first. The steps to enable POP Access in Zoho Mail are available in ‘Enable POP Access’ help page. The configuration details are detailed in the help page ‘Zoho Mail as POP account’
Incoming Server: pop.zoho.com Port : 995
Outgoing Server : smtp.zoho.com Port: 465
Security type : SSL
Outgoing Server requires authentication. The credentials are same as your Zoho account credentials.
You can disable POP Access of your account anytime by clicking ‘Disable’ in the POP/IMAP/ Email Forwarding Settings page
You are trying to configure your account as POP without enabling POP Access for your account. Enable POP access for your account and try again.
When you access the same account from multiple POP clients simultaneously, you may get this error due to concurrent requests. Disable the account in the clients which is not currently in use.