Fighting sp_send_dbmail error: "Failed to initialize sqlcmd library with error number -2147467259."

We recently encountered a bunch of problems with sp_send_dbmail, and they all returned this:

Failed to initialize sqlcmd library with error number -2147467259.

Super irritating, that error, because it seems to suggest that you're doing something you're not. In fact, this error only indicates that there's some generic problem sending mail with sp_send_dbmail. Here are the problems we uncovered, and the troubleshooting steps for them.

1.  The SQL Server service account didn't have sufficient privileges on the domain.

As a rule, we don't allow our domain accounts to query the properties of other accounts.  This is true for service accounts, as well.  SQL, to do a fair number of things (not least to ensure the SQL Agent job owner is a valid domain member) requires the ability to query domain account properties.

We discovered this in troubleshooting:  when trying to use the

execute as user=

statement to make sure we didn't have a problem with database permissions, we received this error:

Could not obtain information about Windows NT group/user...

Aha: domain permissions problem.  This was causing the "Failed to initialize sqlcmd library" error.
Granting the service account additional privileges on the domain fixed this problem.

2.  The executing user didn't have sufficient privileges in the query database.

Having fixed the "execute as user" problem, we can now impersonate a DB user to execute the query in SSMS.  If you have sufficient permissions on the instance.  We're assuming you have sysadmin access, here.

When we run the sp_send_dbmail, and the executing user doesn't have permissions on the target database, we will see the "Failed to initialize sqlcmd library with error number -2147467259." error.

We can uncover this is the problem by just executing the query portion of the sp_send_dbmail stored proc, and using the "execute as user=" statement beforehand.  Specify the SQL Agent service account user in this statement, and if the user doesn't have permissions, you'll get an error message that's actually useful.

3.  The query is executing in the wrong database.

You actually see this pretty often, and the solution to this is most frequently listed possibility for fixing the "Failed to initialize sqlcmd library with error number -2147467259" error. 

The easiest solution to this problem is to specify the target database in sp_send_dbmail, like this:

EXEC msdb.dbo.sp_send_dbmail @recipients = @EmailList
       ,@execute_query_database = 'target_db_name'
       ,@subject = 'Subject'
       ,@body='Here's the body of the email'
       ,@query = @querytext
       ,@profile_name='email_profile'

I hope this helps; we spent far too long on tracking down #1 above.