Start With Filters and Blocked Addresses
The way to mark a specific email address or domain as allowed is to make an email filter.
Start With an Email Message
You can also start the process of making an email filter in Gmail from a message from the person you want to add to the allowed list.
Additional Gmail Filtering Tips
When creating filters in Gmail, keep these additional points in mind.
When you add an email address or domain in Gmail, the filter doesn’t apply to messages already received. It works from the time you enable it onward.If you’re considering allowing an entire domain, think about the possible consequences. For example, if you allow @gmail.com, every single email from a Gmail.com address will be prevented from going to the Spam folder. Yet, there’s a good chance that some messages from @gmail.com addresses should indeed go there. It makes more sense to allow a company you do business with when, for whatever reason, messages from individuals at that company tend to end up in your Spam folder.Another way to mark emails as not being spam is to use the Not spam button. However, this button is only visible when a message is opened from the Spam folder. In other words, you cannot use this method to proactively prevent messages from getting marked as spam.
