I had the the same issue today and it turned out there was an invalid ID in the mailing list. sysmail_allitems was showing it was triggered once but were...

We have had a MSSQL database for data warehouse of size 1.5TB and recently with the purging and arching we were able to cleanup some data and now we have...

Yes, Table has a clustered index and we did rebuild the index so I think we are good. Thanks for the help.

Thanks,

Deep