Jon Steinhart <[EMAIL PROTECTED]> wrote:
>Hi. I'm working on some mail filtering software that will work with
>nmh. I've noticed a few conflicts between the way messages are stored
>in folders and RFC822. I figure that y'all know something about this,
>so just wanted to check to make sure that this is really the case and
>that it isn't a problem or might be a problem in the future.
> 1. RFC822 says that header fields end with a CR-LF pair. That might
> be true on a Microsoft system but not on Linux of any of the other
> UNIX-like systems. Single CR or LF characters are allowed in
> header field-bodies. Does this ever occur in real life or might
> it happen some day?
RFC822 defines what goes out over the network. It does not define what will
be the message format in a user mailbox.
With most unix email software, line termination is converted to CR-LF
on sending the message. The receiving software turns the message
back into the unix NL line termination.
For mail received with a single LF in a header, that LF would be
treated as a unix NL (it's the same character), and the header might
then look broken. A single CR is probably unaffected by most unix
email software. Practically speaking, problems from this are rare or
non-existent.
> 2. RFC822 allows the NUL character in header field-bodies. Code
> written around the C string functions won't handle this of course.
> Does this ever occur in real life or might it happen some day?
Both "sendmail" and the version of "mail.local" distributed with the
current sendmail handle NUL correctly. I have (once) received a
message with NUL characters. MH, and most other unix software,
bungles this because of the problem you mention with the C string
functions.
This is usually not a serious problem in practice. But mostly we
won't notice, since the NULs will disappear from our mail.
>Now, I recognize that this stuff is sort of covered by the NETWORK-SPECIFIC
>TRANSFORMATIONS section of RFC822 but I have trouble believing that any
>*NIX mail system actually does it. Is this true?
Certainly "sendmail" does conversions between network line termination
and unix line termination. I would assume that most other MTAs
do likewise.
-NWR
