[exim] strange connection closed message right after data

Hi all

I've googled around the archives, but found no answer to my problem.
Hope someone can help with this.

I compiled exim from source a long time ago on my home network:

Exim version 4.10 #1 built 21-Nov-2002 03:12:00
Copyright (c) University of Cambridge 2002

so it's not a vendor specific binary.

i have an exim config which i haven't touched for over a year now (from
the exim.conf's timestamp). worked fine with smtp auth over tls, using
mysql as backend.

suddenly today this happened:

[ka@mayten ka]$ telnet mail 25
Trying 10.9.1.8...
Connected to mail.
Escape character is '^]'.
220-Hello, nice to meet you
220 SMTP Daemon Ready.
ehlo thisisme
250-mail Hello thisisme [10.9.1.5]
250-SIZE 5000000
250-PIPELINING
250-AUTH LOGIN PLAIN
250 HELP
AUTH PLAIN adFk3dfdADszMa1=
235 Authentication succeeded
mail from: adamk@mail
250 OK
rcpt to: adamk@mail
250 Accepted
data
Connection closed by foreign host.

This is strange to me, i've never saw an exim closing connection like
this. This config worked for one year now, using it from outlook as
well as from thunderbird.

The server which exim runs on has sufficient resources, almost empty
partitions, no high load, working sql database. And all the letters are
coming in fine! I'm just unable to send, which makes me crazy. I
suppose if the auth part was wrong, it would not say me that 235 auth
succeeded (i see the queries in mysql.log, all works fine).

I have no paniclog, because i have no panic errors (the first error
would create the file) and mainlog, rejectlog shows no errors whatsoever
(rejectlog was created by exim at the first rejected message, so the
user has the rights to create logfiles).

Running exim with -d -v shows that sender user is looked up fine, auth
succeeds from sql, and then:

SMTP>> 250 Accepted
SMTP<< DATA
SMTP>> 354 Enter message, ending with "." on a line by itself
search_tidyup called
close MYSQL connection: localhost/auth/auth
child 2424 ended: status=0xb
0 SMTP accept processes now running
Listening...

This looks like exim is sending the message "354 Enter message,
ending..." to the client, but the message never reaches the client
(tcpdump is not showing either, so it seems that exim thinks it printed
the message to the client, but instead FIN,ACK is sent, terminating the
connection).

Thank you for any comments.
Adam