How to whitelist an email address with Gmail Tutorial

1- Sign in to your account at Gmail.com and do the following.

2- In Gmail, navigate to the spam folder search for emails containing the domain you wish to whitelist (eg onlinegroups.net). Select all the emails shown. Click More and then Not spam.

3- Click the cog icon in the top-right corner, and then Settings
Click on Filters and then Create a new filter
Either enter the domain of the email you want to whitelist in the From field or
enter the email address of the online group you want to whitelist in the To field Click Create filter with this search In the box headed When a message arrives that matches this search select Never send it to spam
Click the Create filter button.

4- Do not enter email addresses in both the From and To fields as Gmail will only filter in emails that meet both criteria
In both the From and To fields, you can enter either a specific email address or an entire domain
To enter multiple domains in each field separate them with OR as in “onlinegroups.net OR groups.yahoo.com”
See also Google’s help on Legitimate mail is marked as spam.