User-Agent: Opera/9.80 (X11; Linux i686; U; en) Presto/2.2.15 Version/10.00 Build Identifier: Thunderbird 2.0.0.22 Application/octet-stream attachments may only be saved, but not viewed. Other file types can be viewed as well - in case Thunderbird does not have a configured viewer, I have the option to chooser a viewer program. Application/octet-stream type should not be handled differently. An application/octet-stream file can be anything. For example, MS outlook sends .log files as application/octet-stream (probably all files with unknown extensions get this MIME type), even though they are plain text files. Reproducible: Always Steps to Reproduce: 1. open a mail view with an application/octet-stream attachment 2 [review]. right-click on the attachment, choose 'Open' 3. a message dialog appears, which says "You have chosen to open <filename> which is a: BIN file from <server> Would you like to save this file?" Actual Results: I only have the option to save the file (or cancel). Expected Results: I should also have the option to view the file (as with standard, known attachment types), with whatever viewer command I choose. Also, it would be great, if the viewer command could be set in the prefs so that I don't have to browse it up again and again.

I see the same in SeaMonkey: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.6pre) Gecko/20091106 SeaMonkey/2.0.1pre - Build ID: 20091106000704 a *.doc attachment erroneously sent (to me by someone else using YahooWebervice) as application/octet-stream could not be opened by "Right-click => Open" in the Mailer. After saving it to disk and displaying the directory in the Browser, "Right-click => Open" (on the link in that directory page) invoked oowriter with no problem.

P.S. And no way to add additional filetypes in "Edit => Preferences => Browser => Helper Applications"

P.P.S. SeaMonkey Mail (2.0.1pre) does not even offer to save the file, it just pops up an alert saying the required application is not available.

I wonder if this is the result of some uncommon broken configuration because I have been suffering this issue for a long time but I cannot find that many complaints in the web or this bugzilla.

Bug 559014 comment 4 following has some worthwhile analysis of these problems provided by WADA.

Removing myslef on all the bugs I'm cced on. Please NI me if you need something on MailNews Core bugs from me.