Is there a limit to the amount of email I can send?
In order to prevent spam, Google will temporarily disable accounts which send a lot of email in a short time. It’s important to be aware of these limits when doing a mail merge. Here are the limits, from Google’s help pages:
-500 messages per day (i.e., you can hit ‘Send’ a maximum of 500 times)
-500 unique recipients per message
-2000 total emails per day (for example, you could send one message to a group of 500 people four times)
In addition to these limitations, Google will temporarily disable your account if you send a message to more than 500 recipients or if you send a large number of undeliverable messages.