"Help" in Outlook Express (version in XP) says as below. Maybe first
step is for your colleague to change settings to not break apart the
message and see if it goes through.
It says "the email program combines them into one message". I don't
know how that works in Outlook. Maybe you have to Outlook express to
receive this mail.
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To send large messages
Many e-mail and news servers limit the size of the messages you can
receive and send. Usually this limit is one megabyte (1 MB) per message,
including all attached files.
With Outlook Express, you can send large messages or files to e-mail and
news servers that have size limits, by breaking the messages into
smaller ones. When the group of messages is received, the e-mail program
combines them into one message.
On the Tools menu, click Accounts.
On either the Mail or News tab, click Properties.
On the Advanced tab, select the Break apart messages larger than x KB
check box and then enter the maximum file size the server will allow.
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Hope this is useful to you. Let us know.
rms