Hello,
I've to apologize.
The empty mail was from my swaks session I did several seconds before
the the netcat session (because I needed the encoded auth tokens).
This swaks line create the empty mail:
</dev/null swaks -d '\n' --body - \
-au <removed> \
-ap <removed> \
-f 'siering@???' -t 'hs@???' -s ssl.schlittermann.de
But this was *intentionally*.
The netcat session started several seconds later and *didn't* generate a message
(I just double checked the sniffed tcpdump file: there I even saw the "lost connection"
from the server side).
The empty-mail-problem still exists, but now I'm quite sure that it's not
caused by exim and/or dropping connections. Even the sending server is some MS
Exchange I don't want to blame it (or at least first I want to be sure that's
not me, generating the empty messages.) They told me that after resetting some
linux router between the Exchange and our server it works for several mails.
But I think it's just coincidence, that router is just router and VPN endpoint...
So again - thank you and sorry for wasting your brains.
--
Heiko