Our dbmail got hosed and I'm trying to resolve the issue.
I've recently recreated sp_send_dbmail, but am not getting an odd error regarding a null value in last_mod_user column in table msdb.dbo.sysmail_mailitems (error 515)
last_mod_user
in msdb.dbo.sysmail_mailitems
should have a default defined on it. Has that gone missing on your install?
ALTER TABLE [dbo].[sysmail_mailitems] ADD DEFAULT (suser_sname()) FOR [last_mod_user]