Block Some Internal Adress - ORF Forums

@dlu: Yes, it is possible by using the Keyword Whitelist feature, i.e. by adding the recipient addresses to the Recipient Blacklist (Configuration / Tests / Recipient Blacklist), but whitelist specific emails by subject by adding a Keyword Whitelist entry (with Subject scope, Configuration / Filtering - On Arrival / Keyword Whitelist, New). The latter whitelisting will apply to all emails though, not only on emails sent to these blacklisted recipients.

Also, please note that this will work only is the Recipient Blacklist test is not excluded from the scope of whitelists in Configuration / Tests / Tests, Whitelist exceptions (Configure button, at the bottom of the page), otherwise the Recipient Blacklist will override the Keyword Whitelist.