my email server is configured with zoho.com with SSL. I had Configured Outgoing E-Mail Settings but OOTB approval workflow give error "The e-mail message cannot be sent. Make sure the outgoing e-mail settings for the server are configured correctly."
Ensure that the mail server is configured to allow anonymous connections from the SharePoint servers. If this has not been configured, the mail server will reject the connection, which will result in the error you're seeing.
You may need to speak to Zoho to have them configure this for you.
To test, try telnetting to the mail server on port 25 from one of the SharePoint servers to see whether the connection is accepted or refused.