User Agent: Opera/9.80 (Windows NT 6.1; U; en-GB) Presto/2.10.229 Version/11.61 Steps to reproduce: Install Thunderbird 10 via auto update over Thunderbird 9.0.1 on Mac OS X 10.7.3 and Windows 7 x64 SP1. Actual results: All email accounts hosted on mail.netenergy.net started displaying "Mail server *email address* is not an IMAP4 mail server." when accessing via IMAP. SMTP also can't connect to mail.netenergy.net and after testing setting up a new account hosted on mail.netenergy.net I found that POP3 doesn't work as well. with error "Configuration could not be verified - is the username or password wrong?" when STARTTLS or SSL is used on IMAP/POP3/SMTP. Expected results: Accounts should have continued to work as with version 9.0.1 and older. After contacting Net Energy it seems they updated their SSL certificate used on mail.netenergy.net days before Thunderbird 10 was released. It would seem Thunderbird 10 doesn't like the SSL certificate. I have tested this in 10, 10.0.1, 10.0.2, 11 Beta and Earlybird 12.0a2 and all have the same problem. A workaround is to select None under Connection security for IMAP/POP3/SMTP.

Could this be bug 723109, ca you try to figure out what server they are using ?

IceWarp as far as I know, I will direct Net Energy to that page.