You can set esoteric SpamSieve preferences by clicking the links on this page. Unlike with regular settings, you must generally quit and re-launch SpamSieve in order for an esoteric preference to take effect.
In rare cases, an Apple Mail bug may prevent the Select Mailboxes to Filter… sheet from showing all of an account’s mailboxes. You can use a Terminal command to tell SpamSieve about one or more missing top-level mailboxes that you want it to show in the list. For example, if account A has a missing mailbox named M and account B has a missing mailbox named N, you would enter this command in Terminal:
defaults write com.c-command.SpamSieve AppleMailMailboxListerExtraMailboxes -array "A|M" "B|N"
When SpamSieve has not been granted Full Disk Access, in order to avoid slowing down or freezing Mail, the Check inboxes for new messages not sent to Mail extension feature will skip filtering an inbox if it contains more than 5,000 messages. Such mailboxes will be shown as orange in the Select Mailboxes to Filter… sheet. In most cases, you should handle this by moving some older messages to the Archive or to another mailbox that you create such as Inbox2. However, if you really want SpamSieve to try to filter a larger inbox, you can change the limit by entering a Terminal command such as:
defaults write com.c-command.SpamSieve MailboxesOutlineOrangeMessageCountThreshold 5000
When SpamSieve has not been granted Full Disk Access, in order to avoid slowing down or freezing Mail, the Filter spam messages in other mailboxes feature will skip filtering a mailbox if it contains more than 10,000 messages. Such mailboxes will be shown as red in the Select Mailboxes to Filter… sheet. In most cases, you should handle this by moving some older messages to the Archive or to another mailbox that you create. However, if you really want SpamSieve to try to filter a larger mailbox, you can change the limit by entering a Terminal command such as:
defaults write com.c-command.SpamSieve MailboxesOutlineRedMessageCountThreshold 10000