I am not personally familiar with this change, but found an FAQ which says: <blockquote><p><strong>If you previously accessed your mail on the Verizon platform,</strong> you do not need to change your POP/SMTP server settings. However, if you entered a different password for your mailbox during the migration to AOL Mail you will need to update your settings with that password. Note: Passwords used on verizon''.''com to access additional services are not impacted by the email password change.</p> <p><strong>If you previously accessed your mail on the Yahoo platform,</strong> you will need to change your settings to use email applications such as Outlook, Thunderbird or the email app on your mobile device to access AOL Mail. Please follow the steps in the help article, "[https://help.aol.com/articles/how-do-i-use-other-email-applications-to-send-and-receive-my-aol-mail How do I use other email applications to send and receive my AOL Mail]". Note: Passwords used on verizon.com to access additional services are not impacted by the email password change.</p></blockquote> ''Source: https://www.verizon.com/support/consumer/email'' Please don't make any changes just yet. Question #1 is: In Thunderbird, are your server settings to retrieve mail currently contacting Yahoo mail servers? And Question #2 is: Is your account set up as a POP account or as an IMAP account? (You cannot switch an IMAP account without the potential to lose data, you need to make a separate local copy of your mail first.) I'm not a Thunderbird guru, so if this is not obvious from your current account settings, someone else hopefully can point out where to look.