SharePoint 2010 workflows triggered by an item added are fundamental to many business processes such as approval and document routing. Unfortunately if a list item is added via incoming email in a default configuration this new item will not trigger an item added workflow. This can limit the usefulness of the workflow. Fortunately this setting is easily changed via PowerShell.
To determine what the current setting is for a farm run the following PowerShell commands in an elevated window (each command is one line followed by a return):
If the Value of the property is “False” you can enable it by typing the following commands (again each line and then return):
$spWebService = [Microsoft.SharePoint.Administration.SPWebService]::ContentService
$spWebService.DeclarativeWorkflowAutoStartOnEmailEnabled = $true
Thats it! Items added to lists via incoming email will now trigger item added workflows on the list. For the MSDN documentation of the property follow this link.