On your SharePoint 2010 site actual alert emails sent for items in your list contain unexpected characters when workflow is associated with the items in it. The issue is not with the initial subscription email.
The issue happened only lists based on custom list template. In the list schema we see that the Title column is mapped to ‘nvarchar7’ instead of default 'nvarchar1'. In this case the ‘nvarchar1’ field in the alluserdata table is used to store the workflow status which is ideally used for store Title of the item. Hence, when alert is sent, it sends the unexpected characters in the title of the alert.
Here is how to fix it ..
§ You need to modify the list template to ensure that the Title column is mapped to default 'nvarchar1'
§ Re-deploy the solution package, create a new list based on that template. The issue should not happen with it.
§ For the existing lists that has the mapping to nvarchar7 the issue will still happen. This is expected behaviour as we cannot change the mapping of the existing columns of the list that has been already created and has data in it.
NOTE: Even if we could have been able to change the schema for the existing problem list, the existing data still would have been in incorrect columns from SQL perspective. There by leading to further inconsistency in the list.
§ To rectify the issue with the existing list, the only option is to create a new list based on the correct list template and migrate the data to it from the existing problem list. You can accomplish this either using PowerShell, Object Model Code, Datasheet View, Export and Import from Excel or manually.