Do CCs and BCCs count against my daily SMTP Relay limit?
Yes. Addresses listed in the CC and BCC fields count against your daily SMTP Relay limit. One relay consists of an email message sent to one address using the SMTP service. So, if you send one email message to 30 addresses, it counts as 30 relays.
Relays are counted on a daily basis and your daily allotment is reset each night between midnight and 2:00 A.M., Arizona time.