When you tell thunderbird 3 beta that you want to print to a file, it pops up a dialog whose default file name is ".ps". It should have a reasonable default file name. Something based on the Subject line might be useful, or perhaps just "email.ps", but ".ps" is right out. Also, the settings for this dialog should persist between invocations. I.e., if I print a message to a file in a particular directory in PDF format, then the next time I print to a file in the same thunderbird session, PDF format should be selected and it should be in the same directory I printed into before.
We filed this bug in the upstream database (https://bugzilla.mozilla.org/show_bug.cgi?id=485067) and believe that it is more appropriate to let it be resolved upstream. Red Hat will continue to track the issue in the centralized upstream bug tracker, and will review any bug fixes that become available for consideration in future updates. Thank you for the bug report.