[exim] Workaround for Windows Mail SMTP weirdness?

Hi,

Has anyone already found out what is the newest way of "breaking the
standards" by Microsoft?

What I mean, is the "Windows Mail" email client that replaced Outlook
Express in Windows Vista. While sending emails used to work nicely with
older clients, now sending a message takes an extra ~15 second dead break
"just for something". Something comparable to timeouting a broken dns check,
but it definetely is not about it this time.
Some forum mentioned, that this seems to happen with every Linux-based
smtp-server with Vista clients. Huh?

While it looks obvious that something has been silently changed at client
side, the only way of making things work smoothly is propably to make the
same change at server end too.
I'm running three Exim. 4.6x servers, and now wondering what to do. I'd be
very happy for any advice to fix this... I still hope it could be done with
some changes in exim.conf?

Regards,
Timo