This is best achieved through the webmail access for the account, as that doesn't require TB be running: https://support.mozilla.org/en-US/kb/vacation-response Otherwise, create a template message and then a filter that automatically replies with the template. This method is probably feasible if you prefer to not send automated replies during office hours, but requires more attention to turn it on/off. http://kb.mozillazine.org/Message_templates http://kb.mozillazine.org/Filters_(Thunderbird)