Many system admins set size limits on sent and received emails, but aren’t aware that there are actually three areas to set them in order to effectively control email size. I usually look at a user’s mailbox in Exchange to determine their specific limit and sometimes forget to check the other two areas.
Size limits should be set for the mailbox, receive/send connectors, and the transport service. If you don’t limit mail sizes, the server will likely become overloaded and mail flow will be interrupted. Admins are responsible to set practical limitations on email sizes in order to ensure uptime.
There are many alternative methods to send large files besides crushing your email server, especially when the emails are internal. Shared folders, for instance, can be used to share gigantic attachments within the network as opposed to sending via email.
You can check all three size limit settings by running the following in Exchange Shell on the mail server: Get-TransportConfig