click to settings>general and UNtick the experimental setting for new accounts and then set up the account

Hi, I un ticked the Experimental tab, and now I can enter my password when trying to set up my new Fastmail account. Firefox finds what look like all the right settings, as per the "20290919 TBird config with password.jpg" screen shot. But when I try to continue, I get the following screen "20290919 TBird get emails failure.jpg". When I close this (because it never goes away) I get the following "20290919 Unable to log in at server.jpg" error. Is there another "Experimental" setting I need to untick? David Edwards [edited email from public]

Hi, I now think that the problem is with Fastmail, not Thunderbird. I have 4 PCs (2 Win 11 & 2 Win 7) here in Sandy Bay. Using SMTP for incoming emails, I succeeded in accessing my Fastmail account (therealdedwards@fastmail.com). On the other 2 PCs I get the blank window "20290919 TBird get emails failure.jpg" which never goes away. After I close it, I get the 20290919 Unable to log in at server.jpg" error message. It doesn't make any difference if I use SMTP or POP3 for the incoming mail. When I hear back from the Fastmail ticket I have submitted, I will post another reply. David.