[exim] data timeout on connection

Hi all,

all of a sudden (after a reboot of the machine, but I cannot see a
connection to that) exim produces a lot of

data timeout on (message abandoned) on connection from mx.example.com
[IP] F=<me@???>

in my logs. These are always the same systems, that retry and fail
again. Other systems don't show probs. By the looks this happens in the
rcpt or data ACL, as the F= is available in the log.

I reinstalled last week's exim.conf to cancel recent changes, but this
did not help.

Hope your answers come through ;-) Will follow on the Web archive.

Yours urgently
Hardy