Database mail issues with maintenance plans & scheduled jobs
Database Mail Fails For SQL Server Agent Jobs / Maintenace plans - Why ?
As you are aware Database Maintenance plans are better in SQL 2005 and more better now after Service Pack 2 release with a cumulative hotfix release. Still there are few problems with database mail when the user is intended to use for alerting on the job status or any failure during the Database Maintenance plans execution. Also the issue with SQL x64 bit platform it has been addressed with Service Pack 1 release for 64 bit.
What if the same issue with SQL 32 bit platform, well the option is to restart the SQLAgent once you have setup the Database mail and with a new profile. This is a default behaviour the way Database mail and SQLAgent works and MSSQL looking to change this behaviour in future releases, so more good features are promised within the mailing stuff.
Further to this I have seen questions in Newsgroups and forums referring the error "An attempt was made to send an email when no email session has been established" and to resolve the issue you can restart the SQLAgent. BOL link fyi for the issue.