I have been using Zoho mail for our business for past 2.5 years. We have about 1000 customers. End of each month we send billing statement to our customers automatically through our billing script. Unfortunately your recent spam protection mechanism blocks our business from sending emails to our customers in this pattern. We are not trying to spam anyone. All our outgoing emails are for our legitimate customers only. I don't know the actual limits you have set up on our account but see if you can help increase it. 

Once the account is blocked how long it takes to come back to normal?

Thanks

Kailas

Vrindavan Milk