Issue:
After sending a large volume of emails from KUMOI (Microsoft Outlook), users may find themselves unable to send any further emails.

Details:
If you experience issues such as “Emails stopped being delivered after sending the same content to many recipients” or “Error messages started appearing,” it is likely that Microsoft has flagged your email address as a spam source or suspected it to be compromised. In such cases, outgoing messages may be blocked.

Once this happens, regular email communication may also be restricted unless the Information Management Office intervenes to lift the sending limitation. If you suspect this has occurred, please contact the IIMS Insuiry.

This situation can arise, for example, if you send around 100 emails at once for seminar or club announcements. While under restriction, even regular communication (such as course-related inquiries) may be affected. To avoid such disruptions, please refrain from using your student email account for mass mailing. We recommend using alternative services for such purposes.

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Risks and Measures When Sending Bulk Emails:
Sending mass emails through KUMOI may lead to your messages being treated as spam, significantly reducing the delivery success rate. Major email services like Gmail and Yahoo may automatically route your future emails to spam folders once they detect suspicious activity.

Furthermore, Microsoft—the provider of KUMOI—has announced stricter measures against such email behavior. This means that even the university’s email domain as a whole could be subjected to sending restrictions, making it more difficult for university emails to reach recipients.

Although bulk mailing might seem convenient, it poses long-term risks. We strongly recommend switching to a safer and more reliable email distribution method.

If you need to send mass emails for administrative purposes or club activities, please do not use KUMOI. Instead, consider using a dedicated, paid email distribution service.