If you sent a large volume of emails and are now seeing failures, this is likely caused by your email provider's daily sending limit not a Kolleno issue.
Both Gmail and Microsoft Outlook enforce a hard cap on the number of emails that can be sent per day from a single account:
Gmail: 2,000 emails per day (500 for trial accounts)
Microsoft Outlook / Exchange: 10,000 recipients per day (limits vary by plan)
Once this limit is reached, all subsequent emails will fail until the limit resets including automated workflow emails and manual sends from Kolleno.
⚠️ This limit is enforced by Google and Microsoft directly. Kolleno is not able to override it.
For more details on Gmail's sending limits, refer to Google's official documentation.
What can I do right now?
Unfortunately, once the daily limit is hit, there is no immediate workaround. Your emails will resume sending automatically once your email provider resets the limit (typically at midnight based on your account's time zone).
How do I prevent this from happening again?
If your team regularly sends high volumes of emails, we strongly recommend setting up Custom DNS. This routes your Kolleno emails through a dedicated sending subdomain (e.g. billing.yourcompany.com) rather than through your Gmail or Outlook inbox, removing provider-imposed daily limits entirely.
Benefits of Custom DNS:
No daily sending cap
Faster email delivery at scale
Improved email deliverability and reputation
To get started, contact your Kolleno account manager who will coordinate with your technical team to set this up.