Sending and Receiving large pdf files

We are using Outlook 2000 on XP. We send pdf attachments to our sister
company in Romania who is also using Outlook 2000 on XP. They are not
receiving some of the pdf files - but they appear in our sent box. I did
some experimenting by sending attachments to myself as follows.

Sending 1-6 pages (approx. 2KB) in pdf format: sends fine / receives fine.

Sending 20 pages (approx. 5KB or more) in pdf format: sends fine /
information bar says I am
receiving the email - my inbox blips but nothing shows up. The doc is in my
sent box, but nothing in my inbox.

I experimented by sending this large file out of Outlook to my aol and I
received it okay.

I then sent out of Outlook and opened up Outlook Express and I received it
okay.


Since then, I deleted all my cookies and deleted all my rules - I then
received the large pdf file. I contacted our Romania office to see if they
did the same. They had no rules applied and did delete their cookies. Some
times they receive the files, but sometimes they don't.

I don't understand how to get around this - anybody have any clue as to how
I can remedy this?

Barbara