I'm having trouble re-establishing email accounts in Thunderbird. I managed to drop them in the process of going to version 115; I don't know how but I did. Now when I try to add them back I can get through the process (Tools > Account Settings > Account Actions > Add E-Mail Account) and enter the user name, email address, and mail server names and port settings for the various domains I use. All goes well until the final phase when it tries to validate the password. The final message says "Unable to log in at server. Probably wrong configuration, username or password." I've done everything I know to do to fix this. I've changed passwords, checked, re-checked, verified, checked re-checked and re-verified the domain's POP3 and SMTP server names and port addresses all to no avail. I'm having trouble with my ISP's (grandecommunications purchased by Astound Communications) support on issues with email addresses that use their domain (@mygrande.net) but I'm also having the same problem with gmail domain (@gmail.com) addresses. I would abandon the email addresses if it weren't for the fact that some of the email on servers is critical and needs to be downloaded to my system. Also, I can't log in to some accounts because the companies use 2-step authentication that involves sending codes to my email addresses instead of codes texted to my phone. This has reached near crisis proportions as I cannot reach those companies except online which requires 2-step authentication using those email addresses that I cannot set up again in Thunderbird. I'm willing to take screenshots at each step if that will be helpful. I'm afraid that I've dealt with the problem for so long that I'm making the same mistake repeatedly but not recognizing that I'm doing so. Any help will be greatly appreciated.