I started this topic yesterday but somehow I do not see it anymore so I post this again.

Recently our client stop receiving notification email sent from our Zoho application although we receive it (we cc ourself in the email). According to our client they did not make any changes to their mail server. Anyone have the same issue?

We suspect that somehow the email from Zoho has been blocked. So could anyone tell me what is Zoho mail server IP Address is so that we can remove the block?