First of all, the IP address is generally found in the headers enclosed beween square brackets, for instance, [129.130.1.1]
Finding IP address in Gmail

1. Log into your Gmail account with your username and password.
2. Open the mail.
3. To display the email headers,

• Click on the inverted triangle beside Reply. Select Show Orginal.

4. manually find the IP address, proceed to 5.
5. Look for Received: from followed by the IP address between square brackets [ ].
Received: from [69.138.30.1] by web4587.mail.***.yahoo.com
6. If you find more than one Received: from patterns, select the last one.
7. Track the IP address of the sender

Finding IP address in Yahoo! Mail
1. Log into your Yahoo! mail with your username and password.
2. Click on Inbox or whichever folder you have stored your mail.
3. Open the mail.
4. If you do not see the headers above the mail message, your headers are not displayed. To display the headers,

• Click on Options on the top-right corner
• In the Mail Options page, click on General Preferences
• Scroll down to Messages where you have the Headers option
• Make sure that Show all headers on incoming messages is selected
• Click on the Save button
• Go back to the mails and open that mail

5. You should see similar headers like above
Or if you want to manually find the IP address, proceed to 6.
6. Look for Received: from followed by the IP address between square brackets [ ]. Here, it is 202.65.138.109.
That is be the IP address of the sender.

7. Track the IP address of the sender