I can't figure out what happens when clicking on attachments. PDFs are sometimes opened in Firefox (which is what I want), sometimes the save-Dialogue appears. Same with other document formats e. g. MS Word. Most of the times the save dialogue appears, but sometimes MS Word opens right away.

Generally I'd like to get rid of the save dialogue. There is a download option anyway for attachments, so if I want to save it, I can use this. When I just click on the attachment I want it to open with the associated program.

How can I get Firefox (3.5) /Zimbra to do that?