Emails not delivered when forwarded from student email to mobile phones (550 Unknown user error)

There have been multiple reports of messages not being delivered when forwarding student emails to mobile phones, particularly with NTT docomo addresses.

This issue is not caused by the student email system, but rather by the receiving mobile phone carrier rejecting the messages.
Common causes include:

• Email filtering settings on PCs or mobile devices

• Anti-spoofing (anti-phishing) settings on the mobile carrier side

More information is available on NTT docomo's official site:
https://www.nttdocomo.co.jp/info/spam_mail/easy_setup/

Adjusting your settings on the docomo side may resolve the issue.

Please note that important notices such as course registration, tuition exemption information, and other administrative messages are sent to your student email. Be sure to check your student email account directly on a regular basis.

Thank you for your cooperation.