This has been a very common question I have seen in several forums, related to using database mailprofile for SQL Agent jobs, and I thought will post here. If you run into this issue, it could be due to one of the following and I have also have mentioned below how to get around them. Bottom line is datbase mail works fine with SQL Agent jobs and maintenace plans in SP1 on all platforms.

1. If you see this on 64 bit platform and on RTM build, this is a bug that is addressed in SP1.

2. If you see the below error message, it is known issue and this is because of design that requires SQL Agent to restart, if SQL Agent was started before enabling databasemail and setting a new profile. We are evaluating to change this design of not requiring to restart agent for our future release.

Re: 264] An attempt was made to send an email when no email session has been established
This problem will go away after restarting SQL Server Agent in this case