If you talk about email accounts, one of us must at least own a Gmail account. The simple reason for this is that Gmail is quite handy and the speed of sending / receiving mail is also very fast. In addition, due to linking to Google account, in addition to Gmail, you can use almost all free services that Google provides such as Youtube, Google Photos, …
The simple reason for this is that Gmail is quite handy and the speed of sending / receiving mail is also very fast.
However, if for some delicate reason you do not use the old Gmail account, use a new Gmail account to make your official email address, and you are in need of moving the entire mail. How to do from the old Gmail account to the new Gmail account? The following will be suggestions for you.

Step 1: Access to your old Gmail mailbox via "gmail.com".

In Gmail's mail management interface, click the gear icon and click "Setting".

Step 2: The Gmail settings page appears, click the tab "Forwarding and POP / IMAP".

When the Forwarding and POP / IMAP pages open, check the box "Enable POP download for all mail"in the section Download via POP.

Once you've selected it, scroll down to the bottom of the page and click "Save changes".

Step 3: Now go to your new Gmail mailbox and click on the gear icon, select "Setting".

Then click on the tab " Account and Enter".

Step 4: Continue clicking "Enter mail and contacts"in the section Enter mail and contacts.

The login window appears, proceed to enter the old Gmail account information.

And complete the connection steps as directed.

When you're done connecting, check the items you need and press OK. Mailing process may take several hours or 2 days depending on the number of mail.

Step 5: Finally, go back to the settings page of your old Gmail account and click "Add forwarding address"in the section Forward of the Forwarding and POP / IMAP.

Enter the new Gmail address and follow the authentication steps to complete the setup of forwarding new mail sent from old Gmail.

Don't forget to tick the option "Forward a copy of incoming mail …" and press Save changes to the settings take effect.
Simple as that, wish you success.