In order for us to better investigate this issue you need to add a little more non-personal information. Please add the troubleshooting information to your post To find the Troubleshooting information: * Open Help (or click on three-line-icon and select Help) * Choose Troubleshooting Information * Use the button Copy to clipboard to select all. Do not check box "Include account names"! * Paste this in your post. Please also add the result of these troubleshooting steps to your post *Does Thunderbird work in TB Safe mode (see [http://mzl.la/1k5DWjq Thunderbird Safe Mode])? *Do you use anti-virus and firewall software? What is the version? *Who is the email provider? *Who is the internet provider? *What is the exact error message? *What steps did you take right before this happened? Please post back with this information and any other questions you might have.