I have Thunderbird on my desktop using POP3, no TLS etc connecting to sendmail/dovecot backend. I can see a 48M mail file on the mail server and new email. Thunderbird will not download the email, it was fine a few days ago. This is a new (ish) installation (~2 weeks), windows 11 and a migration from Outlook. I have deleted/rebuild the sqlite DB under the profile as per another thread. After indexing (62K mails in the Inbox) I still can't download any new mail. I see new email on my phone, and it is configured not to delete email on the server. Worked fine for years. I have a IMAP Thunderbird on a RDP server, this sees/downloads new emails fine. Historically I would use this email client when I was on the road, and when I got back to the office I would revert to my desktop and all the email not deleted would just download to Outlook. This has worked happily for years with Outlook and the last few weeks with Thunderbird. I get intermittent 'cannot to smtp/imap server', when this happens I test via 'telnet' using Putty to both servers, it is also fine. There is no 25/110 access attempts from my desktop in the sendmail/dovecot/firewall/fail2ban logs, which leads me to believe no attempt was actually made