Message size limits There are basically three places where you can configure default message size limits on Exchange:
To check your server’s current limit you can open and access them via Exchange Management Console (EMC), however you can use PowerShell as a method for checking message limits as well. Run the following code in the Exchange Management Shell:
get-transportconfig | ft maxsendsize, maxreceivesize get-receiveconnector | ft name, maxmessagesize get-sendconnector | ft name, maxmessagesize get-mailbox Administrator |ft Name, Maxsendsize, maxreceivesize
The last line of the script (Get-Mailbox) returns information only about the 'Administrator' user's mailbox. Replace 'Administrator' with the user name that you want to check. Or, you can omit the username Administrator (and any other username), and the result will be a list by username of all mailboxes that are present on the Exchange along with their respective mailbox size limits (those size limits likely being 'unlimited' because limits per mailbox were not ever set or configured - which is fine too).
get-mailbox |ft Name, Maxsendsize, maxreceivesize
After you get-transportconfig and get-receiveconnector and get-sendconnector, you can use PS Script in the Exchange Management Shell to change the existing message maximum size limits. The following example shows how to change the size of messages accepted by the transport service to 100 MB.
Set-TransportConfig -MaxSendSize 100MB -MaxReceiveSize 100MB
The easiest way (the least amount of typing) to set the maximum message size limits for the exchange send and receive connectors is to log into the Exchange Admin Center as a user with appropriate administrative privileges.
and do the following:
To confirm your changes, open the Exchange Management Shell [PS] and enter the following:
get-transportconfig | ft maxsendsize, maxreceivesize get-receiveconnector | ft name, maxmessagesize get-sendconnector | ft name, maxmessagesize
Open Exchange Management Console Power Shell [PS]. Here is an example that sets the maximum size for sent messages to 50 MB and the maximum size for received messages to 36 MB for the mailbox of James Geek.
Set-Mailbox -Identity "James Geek" -MaxSendSize 50mb -MaxReceiveSize 36mb
Setting Message Size Limits Per Mailbox: