CRLF in attachments being replaced by LF

[Seb James]

On Thu, 2008-07-10 at 10:48 +0100, Seb James wrote:
> On Thu, 2008-07-10 at 02:34 -0700, Neal Morgan wrote:
> > Seb James wrote:
> > > Hi list,
> > >
> > > I have a problem with some attachments being sent to me.
> > >
> > > I am using postfix and MailScanner and SpamAssassin to process
> > incoming
> > > mail.
> > >
> > > The attachments are raw print data, containing escape characters of
> > > various types and also CRLF pairs, as well as formfeeds, and lonely LF
> > > characters.
> > >
> > > Somewhere, the CRLF are being converted to LF, which messes up the
> > print
> > > data (test docs sent to me by customers for testing and problem
> > > resolution).
> > >
> > > I suspect spamassassin, am I right?
> > >
> > > Any way to turn spamassassin off for certain attachment file types,
> > such
> > > as any files ending in .prn and .dat? I know I can deny or allow files
> > > based on file types, but what about spamassassin scanning depending on
> > > file type?
> > >
> > > Thanks in advance for any help,
> > >
> > > Seb James
> > 
> > Just a wild guess - but since SMTP expects <CRLF>.<CRLF> to end the data
> > phase, is it possible that MUA (sending side) is performing this
> > replacement to prevent message truncation during delivery?
> > 
> > Try having the sender zip the file or rename to a type that Windows
> > doesn't consider text...
> 
> Thanks for the reply Neil,
> 
> I think the attachment would be base64 encoded, meaning that the sending
> side wouldn't see any CRLF to strip out.

In fact, now I look back at the messsage source, the attachment transfer
encoding was quoted-printable, rather than base64, so the problems with
CRLF being modified into LF are quite understandable.

&*$&%£ MS Outlook (the MUA here) for allowing users to send attachments
quoted-printable!

> I'm sure this is happening in my MTA, because the same message sent to
> multiple recipients including me and someone receiving their email via a
> different chain (including some Linux based MTA for their domain then a
> Windows mail client) arrived with the attachment different in each case.
> 
> I really want to avoid asking the sender to do anything if I can
> possibly get these mails to arrive intact!
> 
> best,
> 
> Seb
> 
> 
>