SQL Server keeps a log of mail sent via Database Mail and the sp_send_dbmail Stored Procedure.
I find these code snippets useful to view mail history including sent and failed items. You can view address, subject & body, file attachment(s), status, sent date, etc.
All Messages – regardless of status and deliverability
SELECT top 50 *
FROM [msdb].[dbo].[sysmail_allitems]
ORDER BY [send_request_date] DESC
Sent Items
SELECT TOP 50 *
FROM [msdb].[dbo].[sysmail_sentitems]
ORDER BY [send_request_date] DESC
Failed Items
SELECT TOP 50 *
FROM [msdb].[dbo].[sysmail_faileditems]
ORDER BY [send_request_date] DESC
