Should I have 2 or 3 MX records for a GoDaddy domain?

Should I have 2 or 3 MX records for a GoDaddy domain?

I'm seeing conflicting instructions on the MX records we're supposed to add.  One says we should have two as follows:

mx.zoho.com        10
mx2.zoho.com      20

Sometimes I see instructions that claims we need three as follows:

mx.zoho.com        10
mx2.zoho.com      20
mx3.zoho.com      30

Which is correct?  I have three right now.  It's been several hours and while I can send email from Zoho successfully I can't receive any.  It's possible my DNS hasn't updated but I want to make sure that I have the right records as well.