[exim] Issue with Larger email deliveries and TLS

Hi

I'm using exim 4.71 from the exim4-heavy Ubuntu 10.4 package and have it set
up pretty much how I want it. However I'm experiencing issues with some
email not being delivered. I test this by sending an email with a 20mb
attachment from my Gmail account to the server.

exiwhat shows the connection as:

4180 handling TLS incoming connection from (mail-yx0-f182.google.com)
[209.85.213.182] id=1PlQDE-00015Q-QE

Than after a period of around 10 mins I get the following in the mainlog:

2011-02-04 18:01:48 1PlPk7-0000pk-P5 TLS error on connection from (
mail-yw0-f54.google.com) [209.85.213.54] (recv): Resource temporarily
unavailable, try again.
2011-02-04 18:01:48 SMTP connection from (mail-yw0-f54.google.com)
[209.85.213.54] lost while reading message data

I have the following settings in my exim4.conf file:
tls_advertise_hosts = *
tls_on_connect_ports = 465
tls_certificate = /etc/exim4/exim.crt
tls_privatekey = /etc/exim4/exim.key

smtp_accept_max = 60
smtp_receive_timeout = 30m

This issue is not unique to Gmail as I am seeing the same in the log file
for other hosts but I can reproduce it using gmail.

Hopefully someone can point me in the the right direction.

Regards
Andrew