The mail sync (MAGE) fails with - "Info Skipping message, size limit exceeded" or "Generic item processing error" (4254772)

The mail sync (MAGE) fails with - "Info Skipping message, size limit exceeded" or "Generic item processing error"

Error found in the MAGE log
"2014-09-08    14:36:04.1951    Px11E8    TxE    A9    C1    M3    Info    Skipping message, size limit exceeded (message size - '108019561', size limit - '41943040', SourceKey - '787466B963019B47ADA9B1DA5F75151302793FDEF7D8')."

or

Error Generic item processing error [Message_ID] | System.Exception: The number of items in the Exchange server’s response () does not match the number of items for which uploading was attempted (20).

BY DEFAULT MAGE processes only 40meg batches or 32 items, whichever is reached first

Migration Agent for Exchange (MAgE) cannot process a message that is larger than 40MB. This limitation arises from the use of the Exchange Server 2013 and Office365 Exchange Web Services (EWS). Please refer to the appropriate Microsoft KB articles for more detail:

For Exchange 2013: https://technet.microsoft.com/en-us/library/hh529949%28v=exchg.150%29.aspx

For Exchange 2016: https://technet.microsoft.com/en-us/library/bb124345(v=exchg.160).aspx

For Office365: Office 365 now supports larger email messages—up to 150 MB - Microsoft 365 Blog

In particular, note the following extract from the article explaining the differences between the configured limits and real message limits:

For all message size limits, you need to set values that are larger than the actual sizes you want enforced. This increase in values is necessary to account for the inevitable message size increase that occurs after the message attachments and any other binary data are Base64 encoded. Base64 encoding increases the size of the message by approximately 33%, so the values you specify for any message size limits are approximately 33% larger than the actual usable message sizes. For example, if you specify a maximum message size value of 64 MB, you can expect a realistic maximum message size value of approximately 48 MB.

The maximum size of a message which can be processed by the Migration Manager agent is also stored in the Migration Project. The limit can be set to any desired value but should be lower than the native Exchange 2013, Exchange 2016 or Office365 limit.

To change the message size limit, take the following steps:

1.    Change the native EWS message size limit in Exchange 2013, Exchange 2016 or Office365  according to Microsoft KB articles mentioned above. 

2.    Change the maximum size limit stored in the Migration Manager project with a PowerShell module MMExPowerShell,  as described below. For details, please refer to Migration Manager User's Guide at Migration Manager for Exchange 8.15 - User Guide (quest.com)

To start PowerShell with imported MMExPowerShell module for MMEX version 8.14, on the console computer run the following from the command line:

C:\Windows\SysWOW64\WindowsPowerShell\v1.0\powershell.exe -NoExit -Command "& {Import-Module 'C:\Program Files (x86)\Quest Software\Migration Manager\Exchange Data\Tools\MMExPowerShell\MMExPowerShell' }"

To start PowerShell with imported DMMExPowerShell module for MMEX version 8.13, on the console computer run the following from the command line:

C:\Windows\SysWOW64\WindowsPowerShell\v1.0\powershell.exe -NoExit -Command "& {Import-Module 'C:\Program Files (x86)\Quest Software\Migration Manager\Exchange Data\Tools\DMMExPowerShell\DMMExPowerShell' }"

Important: Only 32-bit version of PowerShell is supported.

Caution: If Migration Manager is installed at path other than the default C:\Program Files (x86)\Quest Software\Migration Manager, change the above command accordingly.

Examples:

For MMEX 8.13:

To increase size limit of target Exchange messages processed by MAgE to 100 MB, run:

Set-DMMExProjectOptions –SizeLimitInMbPerBatchUploadToExchange 100

To increase size limit of Office365 messages processed by MAgE to 100 MB, run

Set-DMMExProjectOptions -SizeLimitInMbPerBatchUploadToO365 100

For MMEX 8.14:

To increase size limit of target Exchange messages processed by MAgE to 100 MB, run:

Set-MMExProjectOptions –SizeLimitInMbPerBatchUploadToExchange 100

To increase size limit of Office365 messages processed by MAgE to 100 MB, run

Set-MMExProjectOptions -SizeLimitInMbPerBatchUploadToO365 100

Note: 

SizeLimitInMbPerBatchUploadToExchange/O365 should be no larger than 75% of the value set in Exchange for maxAllowedContentLength because exceeding this value will cause "The request failed with HTTP status 507: Insufficient Storage" errors, as the MAgE batch size will breach maxAllowedContentLength once Base64 encoding overhead is taken into account. 

*Please note experience in the field has demonstrated that the 33% figure may require increasing further.  To ensure no limitations it may be beneficial to set a figure up to 100% of the desired maximum message size, for example where the desired maximum message size is 50MB a configured limit of 100MB on EWS will increase likelihood of the limit not been reached.* 

It may also be required to increase the MaxSendSize and MaxReceive size of the mailbox using the following command: Set-Mailbox “UserMailbox” –MaxSendSize 40MB –MaxReceiveSize 40MB As well, if the message has already reached the default of 3 retries - the limit will need to be increased using the following PowerShell command once the module has been imported (steps in resolution section): For MMEX 8.13: Set-DMMExProjectOptions -MaxFailedItemRetryCount 6 For MMEX 8.14 and 8.15: Set-MMExProjectOptions -MaxFailedItemRetryCount 6