Sign in to your account at Gmail.com
and do the following. Add the address to your contacts
Add the email address
that is sending you email (eg firstname.lastname@example.org) to your Gmail Contacts. Google will usually deliver email from addresses that are in your Contacts. Mark messages as 'Not spam'
If Gmail has marked emails you wish to whitelist as spam, tell Gmail the emails are not spam.
- In Gmail, navigate to the spam folder.
- Search for emails containing the domain you wish to whitelist (eg mariposa.hn).
- Select all the emails shown.
- Click More and then Not spam
Create a filter for the address
Create a filter to tell Google to whitelist email from a domain or online group.
- Click the cog icon in the top-right corner, and then Settings
- Click on Filters and then Create a new filter
- 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
See also Google's help on Legitimate mail is marked as spam