[exim] HELO vs. EHLO - what does Exim send?

We're having problems sending messages to a particular mail server,
which presents itself as


Microsoft ESMTP MAIL Service, Version: 6.0.3790.0

Error message is

2005-05-04 09:52:46 Remote host xxx [...] closed connection in response
to HELO ...

I suspect the problem is related to the fact that the server does not
understand the EHLO command. When presented with this command, it does
not return an error message, but closes the connection instead.

Is this a correct assumption? What commands exactly does Exim (version
4.3x) send initially?

- Toralf