Probably not a good idea to have the retention period that high, but doing a rough
"guestimate", assuming a MAL record is 200 bytes, assume 10 records cut per email as it flows through the system, you get something like:
200 x 10 x 10,000 x 100 = 2 billion, so round it up to 2 gig.
What else have you looked at? Mail queue sizes? content quarantines? informational folders? What were the results of the command he asked you to run?
BTHW: it is a national holiday today and tomorrow in the US and this is an informal forum, where we all, voluntarily, try to help each other out.
If this is a serious issue for you, then you really should open a support ticket, where there are SLAs guaranteeing response time, etc, etc.