[exim] SMTP Timeout

Dear List members,

I have a problem with my Exim configuration.
I currently have my home mail-router running Exim 4.50 and my remote
server running Exim 4.62.
My home mail-router receives mail from my home-network, forwards it
(TLS encrypted, Auth-Plaintext) to my remote server (because my home-
box has a dial-up IP which many providers reject), and my remote
server delivers the mail then.

As I wanted to send a somewhat bigger mail I got the following
problem (maillog on my home-machine):
2006-07-02 21:32:20 1Fx7g3-0007d8-Q5 <= frederik@???
H=localhost [127.0.0.1] P=esmtp S=1353255 id=047ECBE9-
E916-40BC-9B10-1D66C7807B52@???
2006-07-02 21:37:22 1Fx7g3-0007d8-Q5 SMTP timeout while connected to
mail.freddym.org [62.75.171.23] after sending data block (8189 bytes
written): Connection timed out
2006-07-02 21:37:22 1Fx7g3-0007d8-Q5 == recipient@???
R=smarthost T=remote_smtp_smarthost defer (110): Connection timed
out: SMTP timeout while connected to mail.freddym.org [62.75.171.23]
after sending data block (8189 bytes written)

The corresponding entry in the logfiles of my remote servermachine
looks like:
2006-07-02 21:37:22 SMTP data timeout (message abandoned) on
connection from (server.freddym.org) [84.151.96.216]
F=<frederik@???>

When I triggered a redelivery be entering exim -qff, I got the
following message:
2006-07-02 21:46:27 Start queue run: pid=29391 -qff
2006-07-02 21:52:46 1Fx7g3-0007d8-Q5 TLS send error on connection to
mail.freddym.org [62.75.171.23]: Error in the push function.
2006-07-02 21:52:46 1Fx7g3-0007d8-Q5 mail.freddym.org [62.75.171.23]:
Broken pipe
2006-07-02 21:52:46 1Fx7g3-0007d8-Q5 == recipient@???
R=smarthost T=remote_smtp_smarthost defer (32): Broken pipe:
mail.freddym.org [62.75.171.23]

The corresponding entry in the logfile of my remote machine looks the
same like the previous one.

On successful messages (not the mail I was talking about previously,
this one is still in my mailq, undelivered), I see the following
entry in the logfile:
2006-07-02 21:52:47 1Fx7lf-0007dL-DI => successful@???
R=smarthost T=remote_smtp_smarthost H=mail.freddym.org [62.75.171.23]
X=TLS-1.0:RSA_AES_256_CBC_SHA:32
2006-07-02 21:52:47 1Fx7lf-0007dL-DI Completed

When I triggered a redelivery (-qff) again, I got the same problem as
the first time.

The mail has a size of 1.3MB, but delivering already stops after 8189
bytes (according to the logs), so this should not be the problem.
Most of the mails do not have that problem, I suspect larger mails
have that problem.

My connection is not a really slow modem line, but a 1 MBit ADSL
line, which should be enough for that purpose?!

I am really stuck on this point - perhaps someone can give me a hint
where to tweak on - would be GREAT!

Thanks in advance and best regards,

Freddy Meerwaldt