Thank you, afoken, it was quite long ago, but I am almost sure that I did try both LF and CR+LF (at $work, we very often have to deal with EOL differences between *nix and Windows). The strange thing is that Outlook removes some line endings but not all of them and I wasn't able to find out the underlying rule leading to that. Also, it seems that Outlook does that not only for mails prepared with Perl under *nix boxes, but even for message written on Windows platforms with an Outlook client.