While this is typically called a safelist, the modern term is safelist.
The safelisting procedure differs slightly different from one email service to the next.
However, there are several effective ways tosafelist your friends in Gmail.

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Add Email Addresses to Contacts
Open your contacts list in Gmail.
The fastest method is just to visit theGoogle Contacts link.
On the Google Contacts page, selectCreate contactand fill out theCreate new contact form.

Google will send any incoming emails from your contact list directly to your inbox.
There’s a quick way to fix that as well.
Open your Spam box by selectingSpamfrom the navigation bar, and find your friend’s email.

You’ll see a Spam label at the top of the email.
Click thexnext to the label to remove it.
From your inbox screen, selectSettings(gear icon).

SelectFilters and Blocked Addressesfrom the navigation links at the top.
SelectCreate a new filter.
In theSearch mailform, enter either an entire domain you want to safelist or a specific email address.

Use domains to safelist anyone from a specific company.
When you’re done, selectCreate filter.
On the next form, selectNever send it to Spam.

Finally, clickCreate filter.
Once you’re done, you’ll see the new filter show up in the list of filters.
How to Safelist Yahoo Emails
Safelisting an email address in Yahoo is similar to Gmail.

Either add the email address to your Yahoo contacts orcreate a filter.
SelectNew Contactin the left navigation pane.
Complete theAdd Contactform with your friend’s name and email address.

SelectSaveto save the new contact.
Yahoo will no longer place incoming emails from this email address to your Spam box.
Select theGear iconin the upper right corner of your inbox and click or tapMoreSettings.

SelectFiltersfrom the left navigation menu thenAdd new filters.
SelectSavetwice to activate the new filter.
The filter now appears in the list of filters in theFilterswindow.

This filter move the incoming email from that address directly to your Inbox by default.
Outlook Safelist Procedure
If you’re an Outlook Online user, safelsiting your friends is similar.
Add Contacts to safelist friends or use the Safe Senders feature.

Add Contacts in Outlook.com
Adding contacts is just as easy as Gmail or Yahoo.
Open your Outlook Online contacts by clicking theApplications iconat the upper left corner of the window then select thePeopleapplication.
bang out theFirst Name,Last Name, andEmail Address.

When you’re done, selectCreateto create the new contact.
Any email address listed in your Outlook contacts won’t go to the Spam folder.
UnderSafe senders and domains, click or tapAdd.

In the pop-up field, add an email address or entire domain to add to your Safe Senders list.
Press theEnterkey when you’re done.
Click theSavebutton to finish.

Any email from an address or domains in the Safe Senders list go directly to your Inbox.
For this reason, many people may need to safelist their friends using that service.
If you sign up for it, Xfinity provides customers with a free email account.

There are several ways to safelist your friends with Xfinity.
To add an Xfinity contact, log into your email account and selectAddress Bookin the top menu.
Then, select theCreate Contacticon.

Complete and save the form.
When you click onAddress Book, you’ll see anImport contactslink in the left navigation pane.
Select thegear iconin the upper right corner and click or tapSettings.

SelectFilter Rules, underMailin the left navigation pane, then theAdd New Rulebutton.
Make theRule Nameyour friend’s name.
In theContainsfield, punch in the email address or domain to safelist.

Select theAdd actionlink thenKeep.
Save the new rule.
Once you’re done, you’ll see your new filter show up underMail Filter Rulesin Xfinity Mail configs.

Every other incoming email will be discarded.
However, enabling this feature prevents anyone else from ever being able to send you an email.