[imp] Problems with Word and Excel files attachments

[PatriciaCastañeda]

I have:
RedHat 8.0
Apache 2.0.40-8
PHP 4.2.2-8
Imp 3.1.1
Horde 2.0
Pear 4.1.0

When I send a message with an .doc or .xls attachment, the message
arrives with two attachments: the first with a size more larger than the
original and is not  possible to edit it
( with MS Word), and the second, is with size 0 bytes.
I can send messages with attachments like .c or .php or .html and it is
fine.
What I need to install for resolve the problems with .doc and .xls
attachments?

Thanks,
Patricia C.