I have just upgraded to Thunderbird 115.0.1 and e-mail are not being sent. On investigation Thunderbird is not sending 'Quit' after receiving the '250 Ok' from the SMTP server. Thunderbird thinks the exchange is complete but the socket is still open and the SMTP server is hanging waiting for the 'Quit' response. I have turned on the SMTP debug in Thunderbird and I have captured a typical interaction: Trying to load /usr/lib/thunderbird/libotr.so OTRLib.sys.mjs:65:11 Successfully loaded OTR library /usr/lib/thunderbird/libotr.so OTRLib.sys.mjs:73:13 mailnews.smtp: Sending message <b0371ddc-d1f6-ed22-41b3-42277ac627eb@ntlworld.com> SmtpService.jsm:88:18 mailnews.smtp: Connecting to smtp://eric:25 SmtpClient.jsm:123:19 mailnews.smtp: Connected SmtpClient.jsm:387:17 mailnews.smtp: S: 220 Eric SMTP Server Ready SmtpClient.jsm:416:17 mailnews.smtp: C: EHLO [192.168.0.2] SmtpClient.jsm:591:19 mailnews.smtp: S: 250-Eric offers TWO extensions: 250-SIZE 512000000 250 HELP SmtpClient.jsm:416:17 mailnews.smtp: Possible auth methods: SmtpClient.jsm:878:17 mailnews.smtp: C: MAIL FROM:<me_name@ntlworld.com> SIZE=2939 SmtpClient.jsm:591:19 mailnews.smtp: S: 250 OK SmtpClient.jsm:416:17 mailnews.smtp: MAIL FROM successful, proceeding with 1 recipients SmtpClient.jsm:1135:17 mailnews.smtp: Adding recipient... SmtpClient.jsm:1140:17 mailnews.smtp: C: RCPT TO:<me.m.name.SF@gmail.com> SmtpClient.jsm:591:19 mailnews.smtp: S: 250 OK SmtpClient.jsm:416:17 mailnews.smtp: RCPT TO done, proceeding with payload SmtpClient.jsm:1200:19 mailnews.smtp: C: DATA SmtpClient.jsm:591:19 mailnews.smtp: S: 354 End data with <CR><LF>.<CR><LF> SmtpClient.jsm:416:17 mailnews.smtp: Sending 2939 bytes of payload SmtpClient.jsm:559:17 mailnews.smtp: S: 250 OK SmtpClient.jsm:416:17 mailnews.smtp: Message sent successfully. SmtpClient.jsm:1259:21 Any suggestions has to what is wrong ? Thanks