If you had an update and then suddenly cannot send or receive, you need to check your Firewall. '''For example if you are using 'Norton'''' Restart computer in 'Safe Mode with Networking' mode to completely disabled the computer and installed Anti-Virus product. Check if it works now. If yes, this means it's likely your Anti-Virus and/or Firewall controlled by Norton is blocking the port. It is possible that Norton got confused by the Thunderbird update and thinks it is a different program or one part has not got set up correctly so a port is being blocked. Try this first. * Exit Thunderbird - this is necessary. * Start computer as normal. * Access Norton * Under 'Settings' > 'Firewall' > 'Program Control' * scroll down until you locate C:\Program Files (x86)\Mozilla Thunderbird\thunderbird.exe It should say 'Allow', but select 'Custom' from drop down option. A new window opens: Does it say exactly the following: * Thunderbird, Allow, Direction: In/Out. computer: Any, Communication: Any Protocol: All And is the checkbox selected with a blue X ? If no, something is different from the above, eg: Any Protocol does not say 'All' * click on 'Modify' * Actions tab - select 'Allow * Connections tab - select last one -'Connections to and from other computers' * Computers tab - Select 'Any computer' * Communications tab - select 'All' * Advanced tab - select If explicity requested * Description tab - Type Thunderbird * click on all the OK's * Then make sure it says 'Allow' '''If it says all of that already: ''' Do the following to force a resync - select 'Block' and click on Apply and then cick on 'Close' and exit Norton. Then access Norton Firewall again, look for Thunderbird as before and select 'Allow', 'Apply' and 'Close' Now start Thunderbird.