[fetchmail]malformed header problem in IMAP fetch

Hi,

I've been having an occasional problem with fetchmail, where a "problem"
mail causes fetchmail to abort and causes a backlog. Usually, I solve
the problem by using the web front end to the mail server, reading the
mail and then deleting it. I finally decided to track the problem
down and discovered this:

fetchmail-5.9.3/transact.c:484

            if (!isspace(line[0]) && !strchr(line, ':'))
            {
                headers_ok = TRUE;
                has_nuls = (linelen != strlen(line));
                free(line);
                goto process_headers;
            }

The problem occurs due to the header missing the white space
continuation character(s) required. i.e.
References: foo(_at_)bar foo(_at_)baz
foo(_at_)bim

There seem to be a few problems with handling this anomaly that
I don't think are handled very well:

Is it an oversight that headers_ok is set to TRUE, when the headers
certainly aren't ok?

Would it not be better to emit some diagnostic in this case, and also if
readheaders() returns before processing fetchlen characters?

How about a --add-probably-missing-whitespace (or something :) option
if ":" delimiter is missing (which is what I did as a workaround) and
if we haven't read fetchlen yet?

How about an option to skip or delete problem mails?

Cheers,

Paul

ps. Please CC me as I'm not subscribed.