This article explains how to whitelist a domain in the Mac OS X Mail app, which will allow email from specified domains to come through immediately. Instructions apply to Mac OS X Tiger (10.4) and later.
How to Use Apple Mail on Mac (Really)
To safelist all email from a specific domain in the Mail app on Mac OS X or macOS, follow these steps:
From the Mac OS X Mail main menu, click Mail > Preferences.
Enter a name in the Description field, for example 'Safelist: example.com', to identify the new rule.
