Depends upon what you re trying to achieve. If you are looking for a 'out of office' type of response to all emails, then this is best set up via your webmail account accessed via a browser. Otherwise you have to leave your computer logged on and Thunderbird running with internet connectivity for the duration and this is not exactly very secure if you are away from home. If you are looking to respond to particular email address with a template email auto response, then this is set up via 'Message filters'. First you would need to create a template email and store it in the Templates folder. Note: the 'Subject' will also be used to identify that template email. via Menu Bar: 'Tools' > 'Message Filters' or via Mail Toolbar: Menu icon > Message filters > Message Filters * Check Filter for email address is correct * click on 'New' * Give filter a suitable name Apply filter when : * select: 'Getting new mail' * select 'Filter before Junk Classification' If only one condition or all conditions need to be true: * select: 'Match all of the following' If more than one condition, but any could be true: * select: 'Match any of the following' Set condition * eg: 'From' and 'Contains' and 'type email address' to add another condition click on small '''+''' button Set action: 'Perform these actions' * 'Reply with Template' and click on drop down to locate the tremplate email subject. * click on OK * Make sure filter is enabled. set up Filter Logging so you can doublecheck it is working as expected. * click on filter Log' button * select checkbox 'Enable the Filter Log' * click on 'close' click on top right 'X' to close Message filter window All new incoming mail that meets the conditions should get an auto response. You can check what is being filtered via the Filter Log.