Over the last few days I've been setting up a new laptop and got Thunderbird up and running (which I'm now going to try to use exclusively.) I've been using Thunderbird on my laptop for work related e-mails for 4 or 5 years now. One of the issues I've always had with it was handling TNEF encoded messages (aka "winmail.dat") that Outlook insists on sending.
Now this is really a problem with Outlook in that it doesn't always honor the "HTML" format and sometime insists on sending e-mail in Outlook's native format. If you use Outlook, you have no problems. However, every other client will just get the dreaded "winmail.dat" file as an attachment.
In the past I've just used program (like Winmail Reader) to open the winmail.dat file and view the RTF and attachments. However, I decided to search the Thunderbird Add-ons page to see if anyone had developed a better solution and thankfully Aron Rubin has developed the wonderful LookOut add-on.
LookOut automatically converts the winmail.dat into it's associated attachments and creates a RTF file that you can double-click on to open in Word (or your associated RTF application.) This solution works really well, because I know longer have to open the winmail.dat in an external program just to see the attachments.
So kudos to Aron Rubin for this excellent add-on!