Panel allows you to configure mail services on two levels:
Configuring mail account settings. These settings affect mail account only. For example, where to forward received messages or what to do with potential spam. Learn more about possible operations on mail accounts in the section Configuring Mail Account.
Configuring global mail settings. These are subscription-wide settings that affect all mailboxes within a subscription. Say, what webmail system Panel should use, or what to do with mail sent to nonexistent users. These settings may be unavailable in your hosting plan. To get the details on how to change global mail settings, refer to the section(Advanced) Configuring Global Mail Settings.