select OBJECT_DEFINITION(OBJECT_id('sysmail_faileditems'))
AS [processing-instruction(x)] FOR XML PATH('')
Shows sysmail_faileditemsdefinition
SELECT * FROM msdb.dbo.sysmail_allitems WHERE sent_status = 'failed'
Looking at sysmail_allitems. This definition
SELECT ...
FROM msdb.dbo.sysmail_mailitems
WHERE (send_request_user = SUSER_SNAME())
OR (ISNULL(IS_SRVROLEMEMBER(N'sysadmin'), 0) = 1)
, , sysadmin, , .