User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1.13) Gecko/20080316 SUSE/2.0.0.13-0.1 Firefox/2.0.0.13 Build Identifier: 2.0.0.12 (20080226) The name in the From field is split when it contains a comma. For example, if the from header is From: "Doe, John" <john.doe@somewhat.com>, the name only is displayed as Doe, iso Doe, John. When replying to this mail you get 2 addresses : Doe John <john.doe@somewhat.com> It looks like Thunderbird is not looking at the quotes around the name. Reproducible: Always Steps to Reproduce: 1. 2. 3. Expected Results: From: Doe, John