In initial set up of Thunderbird laptop: on the last screen of set up, after entering username and password, Thunderbird set up posts a green background notice: " [checkmark] Configuration found in Mozilla ISP database." When "Done" is selected, a the following yellow background notice is posted: "Unable to log in at server. Probably wrong configuration, username or password." I know username and password are correct; they allow access to email via Spectrum webmail. I am confident configuration is correct [IMAP] \,because that is the configuration I have always used with my Thunderbird account on other computers. Suggestions?