Have been using Thunderbird for years, with no problems. Now on 52.2.0. On 15 June both sending and receiving of emails stopped working. Internet was working, email provider had no problems with servers, checked server settings and checked firewall not blocking. Email provider said "There are no known issues with access mail at the moment, and nothing in your account settings at our end that indicate a problem either. There are no failed logins, so it clearly isn't a password issue, and you would get errors if that as the case anyway". While waiting for further help from email provider the emails started working again on 16 June. Now stopped again on 20 June. Have tried all the same things with no effect. Server settings on POP (not IMAP). Error message for sending is "Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) [mail server] timed out. Try again." No error message when receiving, it just gets stuck at the "Connected to [mail server]" stage and doesn't go any further. I suspect this is a Thunderbird issue, not email provider or internet. Using Norton for antivirus. Any similar reports, or suggestions? Thanks