I've been having an issue recently and I just decided to try to address it today. It was on a development server so I wasn't that concerned with it. My problem was that when errors were happening it wasn't sending out an email letting me know. I check the job to make sure that it was setup to email the error. It was. So then after a little searching I found that in the SQL Server Agent properties there's a setting to enable the mail profile. This wasn't enabled. Once I enabled it and restarted the agent all worked well! Easy fix!