Job notification fails to send emails

This may be another rookie mistake, but I believe it is worth mentioning it here. I have two servers under my administration and one uses maintenance plan to send out emails after a backup operation is done and on the other one I tried to use job notification to send out email to my account when a "move database copies" PowerShell script job is complete. Both servers' email profiles have been set up properly and test emails have been sent successfully too. However, the one with the maintenance plan does send emails successfully every night while the other one with job notification kept silent for quite a few days in a row and I was suspecting the connectivity of the smtp server it uses. But after some research, the reason actually turned out to be a missed configuration check box on the "Alert System" tab of SQL Server Agent Properties. Strangely, on the first server where the maintenance plan is located and used to send out notification emails, this check box is left empty too. So the conclusion is that maintenance plan, which in essence is an SSIS package, does not require this "Enable mail profile" option to be turned on but email-sending jobs do. Also don't forget to restart SQL Server Agent service after the setting is changed.