Gmail Send Limits: 100 people / connection
Gmail Send Rate: 100 people / day
Gmail Attachment Size Limit: 25MB
Gmail Restriction Expiry Method: Recovered within 24 hours after the limit is reached
Gmail will temporarily disable your account if you send emails to more than 500 recipients or if you send a large number of undeliverable messages.
If you use a POP or IMAP client (e.g. Microsoft Outlook, Mozilla Thunderbird or Apple Mail), you may only send a message to 100 people at a time. Your account should be re-enabled within 24 hours.
Please do verify your contacts’ email addresses. It’s also important that everyone you are sending mail to is willing to receive it.
Further reading: Gmail Bulk Senders Guidelines
