Version:           1.8 (using KDE 3.4.0, Gentoo)
Compiler:          gcc version 3.4.3 20041125 (Gentoo Linux 3.4.3-r1, ssp-3.4.3-0, pie-8.7.7)
OS:                Linux (x86_64) release 2.6.11-gentoo-r6

if you receive an email with an attachment and reply to it, the encoding switches to arabic, even if the encoding in the originating email is us-ascii.  example:

i sent myself an email with an attachment and received it with the following headers:

  ...
  MIME-Version: 1.0
  Content-Type: Multipart/Mixed;
    boundary="Boundary-00=_Cb2dCPfzQEXOsOQ"
  ...
  --Boundary-00=_Cb2dCPfzQEXOsOQ
  Content-Type: text/plain;
    charset="us-ascii"
  Content-Transfer-Encoding: 7bit
  Content-Disposition: inline
  <content here>
  ...
  --Boundary-00=_Cb2dCPfzQEXOsOQ
  Content-Type: text/plain;
    charset="us-ascii";
    name="myattachment.txt"
  Content-Transfer-Encoding: 7bit
  Content-Disposition: attachment;
	filename="myattachment.txt"
  ...

i then hit "reply" and received an email with the following headers:

  ...
  MIME-Version: 1.0
  Content-Type: text/plain;
    charset="iso-8859-6"
  Content-Transfer-Encoding: 7bit
  Content-Disposition: inline
  ...

now i'm sure i could have manually selected the encoding for the return email, but it seems to me that the encoding autodetection isn't working right or it would have used us-ascii for the return mail.  i haven't noticed this until recently mainly due to the fact that kmail doesn't complain.  but apparently, outlook users get a little popup that asks them to install arabic font in order to read my emails...  needless to say, clients are getting confused ;-)