Outpost is a communications layer that operates on top of your business email accounts. You may receive unwanted emails (also known as "spam") in your Outpost inbox from time to time. You can mark these messages as Spam within Outpost, but the controls for spam filters exist in your source email account.
For IMAP mailboxes such as Gmail or Microsoft 365 (formerly Outlook and Office 365), marking a message as spam in Outpost will let the host account know that a message was marked as spam. Marking a message in an Outpost-hosted mailbox will have no future effect.
Check with your email provider to learn more about its spam management settings.