To whitelist an email address just means you add them to your approved senders list. This tells this sender that you know and trust them, which will keep emails from this contact at the top of your inbox and out of the junk folder.
How do you whitelist?
Whitelisting is a quick, one-time-only task to ensure the sender of an email gets added to the recipient’s address book or safe senders list. Usually, all you need to do is open an email message and verify the sender can be trusted.
Here are simple instructions...on how to ensure that future emails get delivered straight to the inbox, in some of the most popular email clients:
Apple Mail (OS X and iOS devices)
Both Apple Mail on OSX and Mail on iOS devices have a similar process for adding senders to Contacts. By selecting the From, or Reply-to on an email message, you can choose to “Add to Contacts” or “Add to VIPs.” For Apple mail "add to VIP" to whitelist the sender. The advantage of “Add to VIPs” is that future emails from this sender will be added to a special VIP mailbox in iOS Mail.
When opening an email from a sender, an alert at the header of the message, “Click here to download pictures…” should display. Click this and select, “Add Sender to Safe Senders list:”
After opening an email message, an alert message should display with, “Parts of this message have been blocked for your safety.” Beneath this, click the link with, “I trust email@example.com. Always show content:”
When opening an email message, a “+” symbol should display next to From: and the sender’s name. Select this and an “Add to contacts” pop-up should appear. Select “Save:”
Gmail (Webmail and mobile)
Getting all future emails from a sender to appear in the “Primary” tab (instead of “Promotions”, or elsewhere) is a quick, two-step process. First of all, drag-and-drop the email message from beneath the tab it’s currently filed under, to the “Primary” tab. Once done, a message alert will appear with, “This conversation has been moved to Primary. Do this for all future messages from firstname.lastname@example.org?” Select “Yes:”
Gmail on mobile devices doesn’t provide a way to prioritize messages. However, touching “Show images” then “Always show images from Sender” will ensure that images always display in the inbox.
Android (Default client)
On Android devices, open the email message and touch the picture of the sender that displays before the message. Tap “Add to Contacts.”
Windows Live Desktop
After opening an email message in Windows Live Desktop, an alert in the preview pane with, “Some images in this message are not shown.” will display. Select the link, “Add to Safe Senders list.”
In the preview pane for an opened email message in AOL Mail, select the sender’s From name under the email’s subject line and select “Add Contact” from the drop-down menu: