Thunderbird suddenly cannot send or receive email

Thunderbird suddenly stopped working properly today, 15 September 2026. Webmail for the same email account is working normally: I can both send and receive messages. However, Thunderbird is having problems with both incoming and outgoing mail. • Thunderbird connects to the IMAP server, sometimes very slowly, but then does not retrieve new messages. • Sending a message from Thunderbird fails because it cannot connect to the outgoing SMTP server. • Thunderbird's own update also fails. This has never happened to me before. • I have restarted Thunderbird and also restarted the Mac, but the problem remains. • I have not changed any Thunderbird account settings. The fact that webmail is working normally makes me wonder whether this is a Thunderbird problem rather than a problem with the email service. Has there been a known Thunderbird problem affecting connections to mail servers or the Thunderbird updater, and could these problems be related