KMAil 5.0.1 is unable to open attachments with "#" in their names.
Reproducible: Always
Steps to Reproduce:
1.Rename a file inserting the char # 
2.Send to yourself a mail with the file above attached 
3.Try to open the file attached with an external program like Okular.

Actual Results: The external program will not be able to open the attachment. 

Expected Results: The external program should open the attachment.

Seems that kmail try to rename the attachment replacing the "#" with "%23", but
the file in /tmp/messaggeviewer_xxx/ remains in the original form, so when the
external program try to open the renamed file it complains that the file is not
found.