To track messages that failed because of recipients MaxReceiveSize:
Get-MessageTrackingLog -EventID FAIL -ResultSize Unlimited | where {$_.RecipientStatus -like *RecipSizeLimit*}
To track messages that failed because of the senders MaxSendSize:
Get-MessageTrackingLog -EventID FAIL -ResultSize Unlimited | where {$_.RecipientStatus -like *SendSizeLimit*}