You have chosen to encode attachment names containing non-English characters in a way that is understood by Outlook(tm) and other mail clients that do not support standard-compliant encoded attachment names. Note that KMail may create non-standard compliant messages, and consequently it is possible that your messages will not be understood by standard-compliant mail clients; so, unless you have no other choice, you should not enable this option.
Ingeleseko karaktereak ez dituzten eraskin- izenak Outlook( tm) - ek ulertzen duen eta beste bezeroek onartzen ez duten moduan kodetuko dira. KMail- ek mezu ez- estandarrak sor ditzakeen arren aukera hau ez erabiltzea gomendatzen da.