This issue has existed for quite a while now with newer versions of kmail/kontact. (about the last 3-4 months)
Issue is this: Kmail incoming mail tiff attachments will not open directly with okular. Every time I try to open the attachment, I get the "which program do you want to open this file" dialog and have to type in "okular" "ENTER" to open the attachment.
However, if I forward the attachment or copy to to another mail for sending, I can open it directly in okular without seeing this dialogue.
I have tried many many many times to click "always open this filetype with this program" but it doesn't work.
The strange thing is, for a short time (about 3 weeks ago for a week only) this problem corrected itself. But now, it is no good again.
Any ideas??? Or should I just club the kontact/kmail developers???