https://www.juniper.net/documentation/en_US/junos/topics/concept/utm-antispam-filter-overview.html
Antispam filtering allows you to use both a third-party server-based spam block list (SBL) and to optionally create your own local whitelists (benign) and blacklists (malicious) for filtering against e-mail messages.
Action to Block:
Blocking spam at the connection level ( sender SMTP server IP@ )
Blocking spam at the e-mail level ( email send address is block )