[exim] Connection lost while reading message data

I am having a problem receiving mail from one MTA. That wouldn't
normally be so bad, but unfortunately it's one that I need to receive
mail from. ;) I started receiving reports that anyone from this server
(a university in Hong Kong) was unable to send me mail. In my logs I
noticed:

2005-01-18 08:55:55 SMTP connection from [...hostname/IP] lost while
reading message data (header)
2005-01-18 09:10:04 SMTP connection from [...hostname/IP] lost while
reading message data (header)
2005-01-18 09:12:17 SMTP connection from [...hostname/IP] lost while
reading message data (header)

I have been in contact with the admin of this MTA, but only just enough
to learn that he is using Microsoft Exchange as a mailer, and is not
receiving complaints from any other admins. This is *only* happening
with this one server.

I haven't had a lot of luck researching this online or in the exim FAQ.
How can I go about debugging this? Unfortunately I'm on a virtual
private server that does not allow me to sniff TCP traffic. Is there any
way I can get more information about what's happening here, and where
the connection is being dropped?