[Exim] message_size too small?

If I run "exim -d jpdalbec < /dev/null" on my workstation with quotas
enabled the debug messages show message_size=311. But the message that
arrives in my mailbox is 510 bytes. What's up? I tested this with an
unpatched Exim-4.10 build just to make sure it wasn't my patches.

This discrepancy means that quota_warn_messages may not be sent if the
threshold falls into a gap between message_size and the size of the
delivered message.

Thanks,
John Dalbec