Large MS Word (2003 or earlier) attachments

[cyberverse]

I have been having an issue sending Word files larger than 2MB from my
RoundCube email system.

A few points of interest:

* I can send smaller Word docs (say 500KB).
* I can send Adobe PDFs of the same size (in fact, the PDF I was
experimenting with was the same document as the Word doc that would not
send).
* I can send the same Word docs via Outlook and SquirrelMail.
* My attachment maximum size is 32MB.

Here are the relevant /etc/php.ini settings:

memory_limit = 32M
post_max_size = 32M
upload_max_filesize = 32M

Please advise.

Thank you.