The main benefit of adding a person to your contact list, is to ensure that their messages are received in your inbox.
Below are instructions on how to add a contact to your address book. The instructions below are for the 3 most popular email service providers.

OUTLOOK


Step 1.  Click on People located at the bottom of the left folder pane.

Step 2.  Click on New Contact.

Step 3.  Enter the contact’s information into the fields.

Step 4.  Click Save & Close.

Adding a contact from a previous message that was received from the sender:

Step 1.  Locate the sender’s name at the top of the email and hover your cursor over it.

Step 2.  Hover your cursor over the sender’s name at the top of the email.

Step 3.  A pop-up pane will open, click on Add to Contacts.  

Step 4.  A window will open for this new contact record, click Save & Close. Note: You may enter additional information in the empty fields before you click Save & Close.

GMAIL

Step 1.  Go to contacts.google.com

Step 2.  Click Create Contact located at the top left part of your screen.

Step 3.  Enter the contact’s information into the fields.

Step 4.  Click Save.

Adding a contact from a previous message that was received from the sender:

Step 1.  Open a message from the sender that you would like to add to your Contacts list.

Step 2.  Locate the sender’s name at the top of the email and hover your cursor over it.

Step 3.  A pop-up pane will open, click on Add to Contacts.  

Step 4.  If you like to add more information about this contact, hover your cursor over the contacts name again and click Edit Contact.

Step 5.  After you have finished filling in the additional fields, click Save.

YAHOO

Step 1.  Locate the pane on the right side of the inbox and click on Contacts.

Step 2.  Click on Add a new contact located at the bottom of the pane.

Step 3.  Fill in the fields for the contact.

Step 4.  After you are finished, click Save.