In the recent times I have seen so many people asking the same question in MSDN forums on how do I activate database mail for the use of SQL server agent alerts system. So I am taking a chance to document it by using screen shots which can help others.
Normally what the newbies tending to do is, once they configured database mail they expect the SQL agent to use it for alerting purposes. To be clear on this part we should make sql server agent to use any one of the configured mail profiles of database mail system otherwise the agent is not going to use them