To avoid this issue with the rate limit, forwarding should be set up at the mailbox level via Tufts Tools. Users can change their forwarding settings at https://tuftstools.tufts.edu/cgi-bin/forward
To remove the limit, you have to remove the max recipient limit from Exchange Management Console, and then run a command in the shell to put the mailbox in a different policy. This can be done in any order.
Exchange Management Console:
Open up Mailbox Properties in Exchange.
Select Mail Flow Settings tab.
Delivery Options → Properties
Remove check for Maximum Recipients.
Set-Mailbox -Identity UTLN -ThrottlingPolicy HighVolumePolicy