For Gmail

1. Navigate to your Spam folder and find the email from the sender.
2. Open the message and click the Report not spam button at the top.
3. This moves the email to your inbox and signals Gmail to trust future messages from this sender. 

Add to contacts

1. Open an email from the sender.
2. Hover your mouse over the sender’s name or icon.
3. Click the contacts icon (a person with a plus sign) to add them to your Google contacts. 

Create a filter

1. Click the Settings gear icon and select See all settings.
2. Go to the Filters and Blocked Addresses tab and click Create a new filter.
3. Enter the sender’s email address in the “From” field. You can also enter a domain name (e.g., @example.com) to whitelist all emails from that domain.
4. Click Create filter.
5. In the next window, check the box next to Never send it to Spam, and then click Create filter again. 

For Outlook

Mark as “not junk”

1. In your Junk Email folder, select the message you want to keep.
2. Click the Not junk button in the top toolbar. 

Add to Safe Senders list

1. Click the Settings gear icon and go to Mail > Junk email.
2. Scroll to the Safe senders and domains section and click + Add.
3. Enter the email address or domain you want to whitelist.
4. Click Save.
5. Alternatively, you can right-click an email in your inbox and select Junk > Never Block Sender. 

For Apple Mail

Mark as “not junk”

1. Go to your Junk folder.
2. Find the email and move it to your inbox or click the Not Junk button at the top of the message. This trains Apple Mail’s filter. 

Add to Contacts

1. Open an email from the sender.
2. Right-click the sender’s name and choose Add to Contacts. 

For Yahoo Mail

Mark as “not spam”

1. Go to your Spam folder.
2. Select the message and click the Not Spam button at the top. 

Add to Contacts

1. Open an email from the sender.
2. Click the Add to contacts button next to the sender’s email address.