thescullster wrote:

Corporate email systems (tend to) revolve around Exchange.
In Exchange, all emails and attachments get merged into one big database
file for access by the Outlook clients.

Up to EX2007, there was single instance storage, so there would be one
copy of the attachment shared by all recipients (or a handful of copies
if the recipients are spread across multiple stores). But from exchange
2010, every recipient gets their own copy, so sending large attachments
to large numbers of colleagues will make you unpopular with the exchange
admins.