Better to do it in Batches of 50, give some time and send again. We tested for 500 messages within 5 mins. Did not get blocked. It is not against TOS as it is

Better to do it in Batches of 50, give some time and send again. We tested for 500 messages within 5 mins. Did not get blocked. It is not against TOS as it is using Whatsapp Web. But use it at your own risk