Thunderbird has no built in option to do this. Log into your account at your email providers web mail page. Most, if not all have this function on their site.

https://support.mozilla.org/en-US/kb/vacation-response

1) Create a "Out of Office" message and save as a template. 2) Create a message filter. Tools>Message Filter 3) Select New then enter a "Name of Filter. 4) Match all of the following 5) Date - is before - 8-1-2014 6) Reply with Template - " Name of Filter" 7) Leave Thunderbird open and running. 8) Out of Office message that was saved as a template will be used to reply to all mail received till 8-1-2014