>>> If you did not add a "message_size_limit = 0" to your exim.conf, i
>>> highly doubt that you got that mail in that size. Exim has a build in
>>> limit of 50MB message size.
>>> The message could be increased in size while processing, i.e. due to
>>> configuration mistakes in form of loops or external scripts.
>>> best regards,
>> But I have a limit which is what has me scratching my head.
>> mx1$ grep size exim.conf
>> message_size_limit = 50M
> That is one impressively large spam email!
> Do you have header_maxsize set?
> header_maxsize total size of message header
> You're also probably better off grepping "exim -bP" as that should give
> you the running configuration in the unlikely event that the config file
> isn't the one being used. (Damn you PHP and your zillions of php.ini files!)
> If you do have message_size_limit and header_maxsize both set to
> something sensible and you're still getting a multi-GB message, then you
> may have found a bug.
> The header comes from their system adding a single header for every
> recipient they add to the email. I'm surprised that didn't kill the
> sending system.
header_maxsize was not in my exim.conf. It is now.
mx1# grep size exim.conf
header_maxsize = 1M
message_size_limit = 50M
The spammer has not been back since I reported this, so I'll have to
wait and see if your suggestion fixes the issue.