Override Domain Block

I am hoping I am in the right forum for this question, looking for assistance with Sophos Central Email Security...

When you add a domain to the block list, is it possible to whitelist a single address within that domain? For example, we get a lot of spam from a domain, @example.com, but would like to allow email for joe.smith@example.com (because we regularly do business with him). Can I whitelist just joe.smith@example.com and override the block that's in place for @example.com?