Importing mail from Yahoo to Gmail, almost free of cost

Yahoo Mail has become increasingly spam-ridden, ad-ridden and buggy. I recommend shifting to Gmail for your email.

1. Upgrade your Yahoo Mail account to Yahoo Mail Plus. You need a credit card. Yahoo will charge your credit card for $19.99 for one year of the Yahoo Mail Plus service. (Don't worry, the charge will be reversed a few steps later).
   
   
2. Enable POP access in your Yahoo Mail Plus account.
   
   
3. Mark your messages in all your folders, even the Sent folder, as Unread. There is no easy way to do it. The fastest is however this:
   
   Enable message view of 200 messages per screen. Select All messages on each screen, mark unread, move to inbox, move to next screen.
   
   This way, You can process thousands of messages in a few minutes.
   
   
4. If you use an email client (e.g. Outlook or Thunderbird) for accessing Gmail, make sure you download all your latest email from Gmail NOW. It will be too late after the next step. Do not start your email client till step 11.
   
   
5. When you are done, enable your Yahoo account as an external account in your Gmail settings. In POP3 options, select the option of "Delete message at server after downloading" (or similarly worded option) and to label the downloaded messages with your Yahoo account name (for later searching).
   
   
6. Gmail will transfer messages in chunks of 200-300 messages every 10-15 minutes, and will take a while to transfer all the messages. Do not login to your Yahoo mail web interface during this time, or the process may fail or get interrupted (this is a bug in Yahoo but we will work around it). You can check the progress of your transfer by checking the transfer log in Gmail settings.
   
   
7. Once Gmail log shows no more messages to transfer, login to your Yahoo Mail Plus account, check that there no messages in your Inbox.
   
   
8. Cancel your Yahoo Mail Plus service. Since the refund is pro-rated, you will get a full refund (or an almost full refund). In my case, it seems Yahoo bills in a batch mode. The two transactions of $19.99 and -$19.99 got cancelled out and my credit card did not show any charge at all (which is different from having two entries: $19.99 and -$19.99).
   
   
9. Set up a vacation message in your Yahoo Mail account. Do note that the amount of spam in your Yahoo account will increase exponentially after this step (as spammers will get a reply from you and your email address will be tagged as valid). The vacation message should say something like this:
   
   "Please note that I have received your email and I will check it in due time. However, I now use Gmail as my primary email provider. Please update my email address in your records, and preferably, send me a copy of your email at my new email address. My new email address is: xxxx at gee emm a i ell dot cee o emm."
   
   Set your vacation time to be the maximum possible. I think Yahoo Mail allows a vacation of 4 months for its vacation message setting.
   
   
10. If you use an email client (e.g. Outlook or Thunderbird) for accessing Gmail, you are in some little trouble. Your client will try to download all the thousands of messages just transferred from Yahoo. If you are like me, you don't want that, so do the following:
    
    In Gmail settings, go to the "Forwarding and POP/IMAP settings" and select "Enable POP for mail that arrives from now on."
    
    
11. Now you can start your client. If for some reason, you received a lot of messages in the time Yahoo mail was getting transferred and you really want them in your email client, there is still a slightly cumbersome way to do it.
    
    In your email client settings, change your username for gmail from xxxx@gmail.com to recent:xxxx@gmail.com. Refer here for details. This will download your last month's email (whether or not you already downloaded all the messages of the last month except the messages received today) to your client. This is bad, I know, but still much better than getting thousands of messages which were transferred from your Yahoo account.
    
    Once you are done, you can remove the recent tag from your username in your email client settings.
    
    
12. You are done!