User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:38.0) Gecko/20100101 Firefox/38.0 Build ID: 20150525141253 Steps to reproduce: Launch/Use Thunderbird while system partition is (nearly) full, (one may simulate this by, e.g., dd if=/dev/zero of=fillfile.bin bs=4096) Start editing a message or maybe some other internal activity Actual results: At least on my Mac, TB often crashes in such situations, for obvious reasons without being able to produce a crash report. Expected results: TB should warn on low disk space and exit gracefully if needed.