What is the message stated in the [sysmail_event_log].[description] column if you execute the query below?

SELECT *

FROM msdb.dbo.sysmail_allitems

LEFT OUTER JOIN msdb.dbo.sysmail_event_log

ON sysmail_allitems.mailitem_id = sysmail_event_log.mailitem_id

ORDER BY

send_request_date desc