The functions available in Mail allow the option to include a query of constituents. When including a query, users may see Error: General ODBC Error: [Microsoft][ODBC SQL Server Driver][SQL Server]Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression. Native error:512.
Specifically, this error has been shown to occur when running Envelopes, Labels, and Phonathon forms, or when selecting to Mail only to constituents marked as Head of Household.
Try each of the following steps in order until the error is resolved: