That message means any of the following are not correct:

• User name is incorrect and/or Password is incorrect
• Password and Username are correct, but not for the server settings you are using.

What do you have in your email address after the '@' sign?

Are you trying to set up a pop or an imap mail account?

What OS are you using? Windows, MAC, Linux ?

Hi Toad Hall (1) OS is Windows 10 (2)after @sign is talktalk.net: thnaks for any help

In webmail account using a browser: Check: do you need to select whether you want to use POP or IMAP? Some auto select IMAP, some do not select any and you have to do this first. Either way, make sure whatever is selected is what you want.

I note on the talktalk website they recommend imap, so it may be auto selected. Note: the type you use is down to you. I have some pop and some imap. I have to admit I still prefer pop, but if you need to access emails from more than one device eg: computer at home, computer at work, phone then perhaps imap is better.

Be careful when entering email address and password that all is correct - no typos :)

In Thunderbird

• 'Menu icon' > 'New Message' > 'Existing Mail Account'
• Enter name,
• Enter full email address
• Enter Password (same one you access webmail)
• Select checkbox to remember password
• click on 'Continue'

Thunderbird will attempt to locate configuration settings.

Check them carefully. Do you want 'Pop' or 'Imap' because this determines server settings.

IMAP

• Username: [email protected] = full email address
• Server name: mail.talktalk.net
• Port :993
• Authentication Method: Normal Password
• Connection Security: SSL/TLS

POP3

• Username: [email protected] = full email address
• Server name: mail.talktalk.net
• Port: 995
• Authentication Method: Normal Password
• Connection Security: SSL/TLS

Outgoing mail server SMTP

• Username: [email protected] = full email address
• Server name: smtp.talktalk.net
• Port : 587
• Authentication Method: Normal Password
• Connection Security: STARTTLS

If you need to check all is correct, click on 'Manual Config' Make sure the Username is your full email address.

Additional thread on same subject here. https://support.mozilla.org/en-US/questions/1209009

Success - problem iust that I have no idea how this came about! I have been entering different settings from all over the web and I must have had about 10 permutations - but.... Talktalk is now running in Thunderbird. Thanks to you all for the time you have taken and I can only surmise that I have found a bit of the solution in each reply. Thanks again