This option is part of the drone setup for Apple Mail.
With Train messages in TrainSpam and TrainGood selected, when away from your Mac (or when using a Mac mail client that doesn’t support SpamSieve), if you find a spam message in the inbox, you can move it to the TrainSpam mailbox. If you find a good message in the Junk mailbox, you can move it to the TrainGood mailbox. SpamSieve will process these mailboxes and then move the messages to Junk or to the inbox.
Once you’ve enabled remote training by selecting the checkbox, SpamSieve will automatically create the special TrainSpam and TrainGood mailboxes in each account in Apple Mail. You can move these mailboxes around (e.g. reorder them in the mailbox list or move them into another mailbox), but do not rename them.
As long as SpamSieve filtering for Apple Mail is enabled, SpamSieve will automatically process the training mailboxes about once per minute. You can also tell it to process them manually by clicking the Filter Now button in the Settings ‣ Apple Mail ‣ Filtering window.
Keyboard Shortcuts
If desired, you can set up keyboard shortcuts on any non-drone Macs to make it easier to move messages into the Train mailboxes. In Mail’s View menu, choose Show Favorites Bar. Then drag the TrainGood and TrainSpam mailboxes to the favorites bar. There will then be keyboard shortcuts for these messages in the Mailbox ‣ Move to Favorite Mailbox submenu.
Legacy AppleScript
The Apple Mail - Remote Training script was available for previous versions of SpamSieve and offered similar functionality. We recommend switching to Train messages in TrainSpam and TrainGood, as it’s much more efficient and better integrated with SpamSieve’s settings. You can then delete the old script file (~/Library/Application Scripts/com.apple.mail/Apple Mail - Remote Training.scpt) and the associated Remote Training rule in Mail ‣ Settings ‣ Rules.