GMail InboxDI reader M. Radhakrishnan recently switched from one Gmail address to another one and now wants to transfer all his old emails to the new account. He writes:
By setting up the auto-forward settings in GMail, I've made sure that all new mails I receive at the old address automatically land up at my new GMail Inbox.

But I've been using the old one for quite a while and so have quite a few important mails lying on that id. Is there a way that I can import all existing mails from my old id to the new one at one go so that I can forget about my old id completely.
Well, this is very much possible though you would need the help of a desktop mailing client like Microsoft Outlook, Thunderbird, Eudora, Apple Mail, Outlook express or even your BlackBerry.

Here are the steps involved to transfer emails from one web account to another one:

Step 1. Enable POP access in GMail settings and also configure your desktop email software to fetch email from GMail servers. [Read How to Backup Your GMail Inbox]

Step 2: Hit the Send / Receive button in Outlook to download all GMail messages from your old address locally. The process might take some time so be patient. Once the transfer is complete, you may want to do some cleaup in your Outlook Inbox - delete duplicate messages, useless threads or those with heavy attachments.

GMail Inbox Backup
Step 3. Create an email rule in Outlook that will auto-forward all incoming email to our new GMail address. Click Start from a blank rule, and then click Next. (Check messages as they arrive). Choose forward messages and specify your_new_address@gmail.com. Run this rule now on messages already in your Inbox.

Click Finish and get a cup of coffee. Outlook is now transferring your old inbox messages to the new one.

The above bulk-email forwarding technique can work for Yahoo and Hotmail users as well. Just use YahooPops or HotmailPopper since these email service don't provide POP access for free accounts.