In case that "sendmail.kuins.net" is set as the email transmitting server, emails are delivered off-campus via the virus spam check server and then ones filtered as SPAM are deleted.
In this case, we should notify a sender that the email is not delivered due to the judgement of SPAM, however, we haven't sent a notification to a sender because we have been afraid that it might increase more the number of SPAM due to the email forwarding setting of the sender.
We had many requests that users want to get an undelivery notification and have been considering measures not to place a high load on the server.
As a result, we can provide the notification system now.

From now on, the following email will reach in case that your email is not delivered due to the judgement of SPAM. Please correct the text and resend it if necessary.

The sample of undelivery notification is as follows.

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Subject: SPAM判定されたためメール送信できていません/ Notification of emails filtered as SPAM From: support @ iimc.kyoto-u.ac.jp
To:

あなたが送信された思われる下記のメールがスパムメールと判定され送信されませんでした。
文面を修正して再送信してください。
The following emails you sent are not delivered because they are filtered as SPAM.
Please correct the text and send them again.

Subject: ○○の件よろしく
Date: YYYY-MM-DD hh:mm:ss +0900 (JST)
Rcpt To: user1 @ example1.com

Subject: △△の調査お願い
Date: YYYY-MM-DD hh:mm:ss +0900 (JST)
Rcpt To: staff @ example.com

文面を修正して再送される場合は、以下の点にご留意願います。

- HTMLメールは避けてテキストメールにしてください。
- できる限りファイルの添付を避けてください。
- できる限りURLを記載しないでください。
Please consider the following things when you correct the text.
- Use a text email, not a HTML email.
- Try not to attach a file.
- Try not to write down a URL.

スパムチェックはシマンテック社のシステムを利用しており、本学で判断基準を 変更することができません。 文面を修正して送信してもSPAMと誤判定され続ける場合はsupport @ iimc.kyoto-u.ac.jp までご連絡ください。 このようなメールを送信した覚えのない場合もご連絡ください。
We are sorry but we can't change the criterions for judgement of SPAM because the system and the database are provided by Symantec.
Please contact support @ iimc.kyoto-u.ac.jp in case modified emails still filtered as SPAMs. Also contact us if you have no idea about emails listed above.

京都大学 情報環境機構 情報環境支援センター
ICT Support Center, IIMC, Kyoto University
Email: support @ iimc.kyoto-u.ac.jp