One of the problems IBM Cognos Administrators come across after deploying IBM Cognos, is the question to e-mail excel outputs to the mailboxes of business users.
By default, however, IBM Cognos will not e-mail the output in Excel format, but in .mht format, which makes it cumbersome for users to open the file.
There is a way to overcome this, and it's really quite simple, although you need to know how to do it.
Cognos is made up of a number of internal services. Each of the services has its own settings and properties. The URL below shows a comprehensive overview on how to set the advanced setting "RSVP.FILE.EXTENSION.XLS" on the ReportService and BatchReportService.
Be sure to check it out.
http://www-01.ibm.com/support/docview.wss?uid=swg21385491
Nice to know is, this setting also influences the behavior when writing outputs to disk.