I use Outlook 2007 (and some others in my company). We also use Yahoo! Business Email for our email server.
I've not received some emails from clients and co-workers with XLSM attachments. I would see them on my Blackberry, but then would not see them appear in Outlook. They would disappear from the server after I found them missing from Outlook.
After an hour with a Yahoo! support person, we narrowed down the problem to Outlook. The email would stay on the server until Outlook POPped. The status in the lower right would say receiving 1 of 1 with the size of the email. Then it would complete and the email would be gone; both not appearing in Outlook (even in the Junk folder) and deleted from the server. This is not just happening to me but to other users of Outlook 2007 as well. Our Outlook 2003 users appear to be unaffected. I receive .DOCX files and every other type of attachment.
Thank you, Tony Brubaker