Could you use something other than rar for the attachments? RAR is a commercial format that is difficult to uncompress on Linux.
jrs@Laptop:~/o2h$ unrar AC.rar
unrar 0.0.1 Copyright (C) 2004 Ben Asselstine, Jeroen Dekkers
Extracting from /home/jrs/o2h/AC.rar
Extracting A/A.dll Failed
Extracting A/Fruit.bmp Failed
Extracting A/Win_G.inc Failed
3 Failed
jrs@Laptop:~/o2h$