Are you planning on leaving your computer on and connected to the internet with Thunderbird running all the time you are out of the office. What happens if you have a power outage.? Will your correspondence appreciate getting a reply to each and every mail they send you that you are out of the office. Generally it is agrivating to get lots of out of office responses. Why not use the out of office/vacation response option provided by your providers web mail. Most have one and most will only send a single message to each email address mail is received from in the absence, not one for every email as will happen with a filter.