So hopefully you have moved to databasemail and started enjoying its many benefits. Remember that cool benefit of it logging all the emails for you and such? Well that comes at a price, and the price is an ever growing MSDB. So, you should consider setting a retention date for your servers and create or add the following to your maintenance packages/jobs.
This script will clear out the mail items and the log based on the @Retention_Days variable:
DECLARE @Retention_days SMALLINT , @Delete_Date DATETIME SET @Retention_Days = -90 -- 3 months SET @Delete_Date = DATEADD(d, @Retention_Days, GETDATE()) EXECUTE msdb.dbo.sysmail_delete_mailitems_sp @sent_before = @Delete_Date EXECUTE msdb.dbo.sysmail_delete_log_sp @logged_before = @Delete_Date