Product:
Cognos BI 10.2.1
Windows 2008 R2 server
Outlook Mail program

Problem:
Mail sent is not coming forward to the end user from Cognos BI.
In some cases you get a message from the Exchange Mail server that the mail is
This is an automated message from the Extensible Content Security

A mail from you x to y was stopped and Quarantined because it contains one
or more forbidden attachments.

Summary of email contents:

Attachment: My personal report 1.mht
My personal report 1.mht forbidden file extension (.mht)
My personal report 1.mht forbidden file extension (.mht)
Attachment: html
Attachment: image

Because:
Cognos BI 10.2.1 send mail with Excel 2002 attachments as MHT files, that Excel can open but your mail system may have excluded that be allowed.

If you send a report as HTML and include a Body Text in the Schedule message you will get the same issue, please send a link instead of a HTML attachment to make it work.

Solution:
In Server Administration, add “RSVP.FILE.EXTENSION.XLS” parameter to ReportService and BatchReportService.
Steps:
1. Open Cognos Connection.
2.Click Tools menu in the portal and select Server Administration
3. Check Services for Type (All services appear)
4. Select Set Properties for ReportService
5. Select the Settings tab
6. Find the property named Advanced Settings, and click the Edit… link
7. In the first empty set of boxes, type in the parameter name RSVP.FILE.EXTENSION.XLSand set the value to TRUE
8. Press OK.

More Information:
http://www-01.ibm.com/support/docview.wss?uid=swg21342065