Henrique de Moraes Holschuh wrote: >They REALLY shouldn't, and the MTA is supposed to trash them when told to >not add them in the first place, and to rewrite them with the true >information when told to add them. > > Most MTAs are pretty good about this. However, when using an IMAP client to move messages between accounts (e.g. drag and drag in Mozilla, Netscape, Outlook Express, etc) the source account may well store the "From " in the message even although the MTA did not send it like this. This is where our users were constantly complaining until we added this patch--they would try to drag messages to their Cyrus mailbox from another mailbox and get the cryptic (to them) "Message contains invalid header" error.
While I can certainly understand that accepting non-RFC compliant messages is something that may not be acceptable in a major distribution (at least by default) I can tell you that doing so has substantially reduced our support load in this case. We probably see this problem more often than most sites, because we are a fast-growing public email provider so people are often migrating messages across to us, and also we have a lot of ex-Hotmail users (and Hotmail is one of the providers that store messages with the "From " prepended).
