Mixmax sends your messages through your Gmail account, and because of that, it is subject to any limitations set by Google, including rate-limiting for message sending. Google monitors the rate at which messages are sent through your account, not just the total number of messages you send in a 24-hour period. To learn more, see Google's specific account limits. This means your account could be limited if you send a high volume of messages in a short period of time.
Mixmax has some safeguards in place to help prevent your account from getting rate-limited. If you send your sequence to more than 500 recipients at once, we will space out your sending over multiple days — 500 messages per day — and space out the send times throughout the day. Take a look at some best practices for setting up sequences. Mixmax may limit the number of emails that can be sent by a single user in a day to 1000 to ensure users are not rate-limited by Google (we work with Gmail as the underlying email service). To learn more, see Gmail's specific account limits.
Even with these precautions in place, there is still the possibility that the account will get rate-limited. If your account is rate-limited, we may be unable to send all of your sequence messages. If this happens, we will notify you via email, so you won't be left wondering. If you receive this email, you can re-try the undelivered messages.
How to retry sending undelivered messages
After your account is rate-limited, we recommend waiting for 24 hours before retrying unsent messages to make sure your high-volume sending doesn't raise a red flag again. To retry sending messages, go to the Recipients tab for the affected sequence. The email you received includes a link to the sequence. Click the Recreate button — see the screenshot below:
The system will try to resend your emails, and the send times will be spaced out to minimize the chance of being rate-limited again.