How can i move or copy all of my mails from one Email ID to another in Gmail?

Go into your Gmail settings (Hit the settings button at the top right of the window), and go to the “Accounts and Import” tab. Click the first item on the list, “Import mail and accounts” and follow the instructions there.
At some point, you may have to give the POP server and port number for the service you’re importing from. The server will generally be pop.[whatever the website name is ].com and the port number should be 995. But that may vary. If you use a web service (e.g. hotmail, yahoo, aol) you should be able to find that in the Help/FAQ sections of their site.

@Sarcasm i want to import mails from one Gmail account to another.
so POP server will be pop.gmail.com or what?
and port number 995 ?

For email between two Gmail accounts, you can just go to that “Accounts and Imports” tab and click the “Add POP3 email account” right under where it says “Get your mail from other accounts in Gmail using POP3” and put in the information there.
You may have to manually enable POP3 on the remote account, you can do that by just going to Settings -> “Forwarding and POP/IMAP” on it. But it seems like it’s enabled by default for me.

Just for the record, I have a few accounts that funnel into one. It generally takes about 30 minutes for me to receive an email from those remote accounts in my main inbox. From time to time, from certain people, I won’t get the email for a day or two for whatever reason. So make sure any highly important emails are sent directly to your main account.

@Sarcasm I want all of my old mails to be moved to the new account and not just the new ones.New mails may keep going to the old account,it doesn’t matter much.Will this same method work for that too?

Hi. Don’t know if you’re still looking for an answer but….

Log into your current gmail account.
Go under settings at the top.
Go to accounts and import.
Click import from another address. (You shouldn’t have to change any port numbers)

This is used if you want to import from Yahoo, Hotmail, or other email providers. Try this and see if this works for you.