Comment 9 for bug 259387

I think the problem is nothing to do with the front end but the back end.

In nsMsgCompose::CreateMessage http://lxr.mozilla.org/seamonkey/source/mailnews/compose/src/nsMsgCompose.cpp#1729
because the originalMsgURI used to contain &type=application/x-message-display (which was removed and &realtype=message/rfc822 appended at the end), rv = GetMsgDBHdrFromURI(uri, getter_AddRefs(msgHdr)); returns a failure which means CreateMessage fails.

We should probably remove the NS_ENSURE_SUCCESS, check for a failure and return NS_OK or remove the NS_ENSURE_SUCCESS, check for a success as well as msgHdr and at the end of the function (about line 1983) return NS_OK or something along those lines. I would say the latter because the former would probably cause leakage and there may be multiple uris passed through to be dealt with.