I know I can pass certain SMTP traffic based on the source address, but can I do it based on a domain? For example, Threat Prevention automatically blocks SMTP traffic coming rom iCloud servers (i.e. *.icloud.com and *.me.com), so is there a way I can blanket permit domains like that?
All I can think of to do is base a rule on a condition category like HTTP:URL, but I get the impression that it will only affect web-related traffic.