The TalkTalk settings you need are given here: https://help2.talktalk.co.uk/email-settings-imap-pop3 You will see that TalkTalk recommend that you use IMAP, so I would go with that unless you have reasons not to. Thunderbird will normally default to IMAP when you create a new account but it may not know the correct settings for TalkTalk, so at the least you need to check them. To be sure, you can create an account manually: https://support.mozilla.org/en-US/kb/manual-account-configuration You don't say why TalkTalk are threatening to delete your data. If it's because you haven't used the account for a while, it may have been suspended -- I don't know TalkTalk's policy on this and I'm not a customer of theirs. Before you blame Thunderbird or its settings, I'd suggest that you log into the account via the TalkTalk website: you need to make sure that the account is active and working properly before you try to connect to it with Thunderbird or any other email client.