User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; de-AT; rv:1.8a3) Gecko/20040817 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; de-AT; rv:1.8a3) Gecko/20040817 This From:-header confuses mozilla because of the encoded comma: From: =?iso-8859-1?Q?D=F6rge=2C_Michael?= <someone@example.com> It decodes to "Dörge, Michael <someone@example.com>". The comma, however, is not escaped. MailNews dispay the name "Dörge" in the message list and the string "Michael <someone@example.com>" in the gray bar beetween message-list and message. Answers are sent to Dörge@exmaple.com and Michael <someone@example.com> Reproducible: Always Steps to Reproduce: 1. Receive a mail with an MIME-encoded comma in the from header. 2. Look at the from column in the message list and the gray bar above the message 3. Try to answer the message and have a look at the to-headers. Actual Results: From-header is split at the comma. Expected Results: From-header should be treated as one unit (escaping the comma by putting the complete name in quotes if necessary)

Looks like a duplicate of Bug 254519.

I agree. *** This bug has been marked as a duplicate of 254519 ***