Gmail:

1. To whitelist a sender in Gmail, first open all emails from that particular sender.
2. Hover over the sender's name and you'll see a popup. In the pop-up window, click Add to Contacts.
3. The sender's contact address will be added to your address book/contact list.

Yahoo:

1. Sign in to Yahoo and hover over the gear icon in the upper right corner.
2. Click on Personal Settings
3. On the Settings page, select Filters from the menu on the left
4. Click Address to add a new filter.
5. Give your filter a name in the FilterName field.
6. Select criteria to whitelist emails
7. Once the conditions are set, to then move messages to this folder, select Inbox from the drop-down list.
8. Click the button to save the filter.

Outlook/Hotmail:

1. Click on the Mail Settings icon in the upper right corner
2. Click the Options button
3. In the left menu, click Mail-Junk email-Safe senders
4. In the right menu, add the email address you want to whitelist

Outlook – desktop client:

1. Right-click on the email you want to mark as safe
2. Click Junk and choose Never Block senders or Never Block sender's domain or Never Block this group or mailing list.

1. Right-click on the email you want to mark as safe
2. Click Junk and choose Junk E-mail Options
3. In the pop-up box, click Safe Senders to add the email address
4. After adding addresses or domains to mark as safe, click OK

MacMail:

1. Click Mail and choose Preferences from the top menu.
2. Click Rules to Add Rule.
3. Name your rule in the Description.
4. In the If any of the following sections, select From and Contains. In the blank field to enter the email addresses or domains you want to whitelist.
5. Next perform the following sections, selecting Mobile Messages and Inbox.
6. Click OK to save the rule.