I was unable to receive any messages over 5MB. I had checked all the usual settings, ISP, Receive Connectors, Send Connectors, Transport Rule Limits, and Mailbox Limits and confirmed that they were set to 100MB, both from EAC and also from the Management Shell. I also ran >telnet <exchange server> 25 followed by EHLO and confirmed '250-size 104857600. All email larger than 5MB was returned with the following two messages:
1. Your message is too large to send. To send it, make the message smaller, for example, by removing attachments.
2. Remote Server returned '< #5.2.3 smtp;550 5.2.3 RESOLVER.RST.SendSizeLimit.Org; message too large for this organization>'
The fix for me was to run the following command in the Exchange Management Shell:
>Set-TransportConfig -ExternalDsnMaxMessageAttachSize 100MB -InternalDsnMaxMessageAttachSize 100MB -MaxReceiveSize 100MB -MaxSendSize 100MB
Use Get-TransportConfig to verify your settings.