User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7) Gecko/20040928 Firefox/0.9.3 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.8a5) Gecko/20041011 The bug strikes when replying to an email with a From:-line like this: From: =?iso-8859-1?Q?Martin=2C_Forss=E9n?= <maf@tkrat.org> Mozilla thinks this line contains two addresses while it only contains one. The bug is most likely caused by the comma which is encoded within the encoded word. But as far as I can see the above use is legal since and encoded word can be used "As a replacement for a 'word' entity within a 'phrase'" (rfc2047 section 5 .(3)). Reproducible: Always Steps to Reproduce: 1. 2. 3. When forwarding a message like this inline it shows the from address correctly. The same applies if I try to bounce the message in Thunderbird 0.8.

*** This bug has been marked as a duplicate of 254519 ***