Outgoing mail is blocked but user limit not reached

Outgoing mail is blocked but user limit not reached

I've been trying to update folks in my address book about switching to zoho for email, and sent 4 messages with 25 addressees each, and then the account was blocked with the message
"Dear User, Your Mail Outgoing blocked. Reason :Daily Recipient count exceeds limit [Total Recipients=500"

and I also got another one with
"Dear User, Your Mail Outgoing blocked. Reason :Daily Mail Bounce Count Exceeds Limit [ Bounce count=25 ]"

even though I only got 3 bounces from the bunch that actually got sent.

I am using POP through Thunderbird but don't know why sending a message to 100 addresses would end up being "total recipients=500"?