Here is a quick command you can run from the Exchange management shell which will set the Maximum Send and Receive Size for all users in the specified Distribution Group.
In The Below Example i’m setting the Send/Receive Limit to 100mb for all users in the Distribution Group called DG1.
Get-DistributionGroup DG1| Get-DistributionGroupMember | Set-Mailbox -MaxSendSize 100mb -MaxReceiveSize 100mb
