How to enable POP or IMAP in GMail
Enable IMAP in your Gmail settings
1. Sign in to Gmail.
2. Click the gear in the top right.
3. Select Settings.
4. Click Forwarding and POP/IMAP.
5. Select Enable IMAP.
6. Click Save Changes.
Enable POP in your Gmail settings
1. Sign in to Gmail.
2. Click the gear in the top right.
3. Select Settings.
4. Click Forwarding and POP/IMAP.
5. Under POP Download, select the radio button for Enable POP for all mail or Enable POP for mail that arrives from now on.
6. Click Save Changes.
You can take a look at this article to learn how to use Gmail to send emails from your domain email address.