The Mailboxes | Message Sizes | Sent/Received Distribution reports only counts message sizes up to 20 MB and some organizations might require a bit more detail past the 20 MB range.
Currently the upper limit for recorded message sizes is 20 MB, however larger messages might be received, which are being counted as just larger than 20 MB indiscriminately.
TF00325231 has been created to address this requirement.
