If you are sending an email to over 500 users using the Email Users Tool, it should be noted that there is a limit put into place by Gmail. Admin Tools uses notifications@geo-jobe.com for the default email notifications which is powered by Gmail.
"You may see this message if you send an email to more than 500 recipients in a single email, or send more than 500 emails in a day.
When you get this error, you should be able to send mails again within 1 to 24 hours."
Solution
If you need to send an email to more than 500 users, you may need to break the emails into waves of 500 at a time. Alternatively, you may also set up your own SMTP server, and utilize our option for "Custom SMTP." in the Email Users tool.
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