I already have a gmail email address but cannot access it due to Thunderbird demanding I open a new address

In an article titled, "Email already exists," at: https://support.google.com/accounts/answer/69849?hl=en

Google Help advises:
If you see this message when you try to create or change your account username, it's possible that you've already created a Google Account with that username. It's also possible that someone else accidentally entered your email address when creating a Google Account, but was never able to verify email ownership.
To reclaim your Google Account, please follow these steps:

1. Visit the password-assistance page.
2. Enter your username (your full email address).
3. Type the letters shown in the distorted picture into the appropriate field.
4. Click Submit. You'll receive a message at the address registered as your Google Account username. Follow the instructions in this message to reset your password.

After you've regained access to this account, you can either delete the account, or change the username on the account to another valid email address. You'll then be able to change the email address on your other account to this email address.
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I hope this works for you!

The Settings section of GMail is needed to block SPAM from their webmail.
Click the gear icon, click "Settings", click "Filters", click "Create new filter". Enter words, names, etc., and save the new filter. I haven't tried it and don't know if anything else is needed.

If you use an email client to receive the mail such as Thunderbird, or Outlook Express, you can block individual senders, or create message filters where particular words cause a message to be redirected. Using Thunderbird, I have a filter that sends any email not in my address book to Trash, though I could send it to a SPAM folder or my Purgatory folder. I check each message header before deleting the message permanently. If a sender has a new email address, or hasn't mailed me before, I add them to the address book and they won't be filtered out in the future. But most of the time I see the name of someone I know in the Trash, it's just a scam, SPAM, or malware.

Are you using Gmail web mail or are you using maybe Thunderbird email client to access your Gmail account? They have application-specific passwords.
Google search: gmail password separate from google password

o cancel a Gmail account and delete the associated Gmail address:

• Go to Google Account Settings.
• Open the Products page.
• Click Edit under Your products.
• Click Remove Gmail permanently under Delete a Product.
  • You can also choose Close account and delete all services and info associated with it to remove your entire Google account (including your search history, Google Docs, iGoogle page, AdWords and AdSense as well as other Google services).
• Make sure Yes, I want to permanently delete [email protected] and remove it from my Google account. is checked.
• Enter an email address different from the address associated with the account you are closing under New primary email address.
  • Gmail may already have entered the secondary address you used when creating the Gmail account.
  • The alternative email address becomes your new Google account user name.
  • Make sure you enter an email address to which you have access. You need that access to complete deleting your Gmail account.
• Enter your Gmail password under Current password.
• Click REMOVE GMAIL.
• Open the "Gmail Removal Confirmation" email from "[email protected]" at the email address you specified as your new.
• Follow the deletion link in it.
• Type your Gmail password under Password:.
• Click Verify.
  • Keep in mind that you cannot undo this step.

create a new free gmail account and register facebook there, you can add any other email address to the account once opened when ur old email address is fixed

Hi,
The default email program given with Linpus linux is Mozilla Thunderbird.
If you already have email address in any of the website or domain, you can configure it with Thunderbird. But you need to know the various parameters like Incoming and outgoing mail server address, port addresses, etc.
You cannot configure Free mail services like yahoo with Thunderbird.
You can configure Gmail with thunderbird.
Please read the following link to configure your Thunderbord with your Gmail account.
http://www.ehow.com/how_2337577_configure-thunderbird-work-gmail.html

I hope this is useful to you. Please provide your rating and comments for the solution provided.
Thanks

changing email address will loose only the profile that you created from old email. If your talking about the address book and personal files ( like old emails ). All you have to do is Archive it and open it from the email client (Outlook, Outlook express, Thunderbird, etc.) that you're using from new email address.

Please tell us the email client that you are currently using so that I can tell you where to grab the address book and Personal files from default folder.