Luckily, I got the domain “v6-mail.com”. Logically, the email account for autoreply function is “autoreply@v6-mail.com”. I continued to configure my DNS to handle MX and AAAA records. Next, I installed Postfix on a dual-stack Linux server with 6to4 tunnelling and I forced Postfix to listen to IPv6 address only. Then came the most difficult task. How to enable autoreply function on the user “autoreply”. I used .forward and vacation but the problem is vacation only reply to sender once within a day and any other subsequent email received from the sender will not be replied. I recalled that flushing vacation.db will clear all previous locked records so I added an cron job to do “/usr/bin/vacation –I” on a per minute basis. This solved all problem plus it added anti-spam feature. If the sender sends more than one request to “autoreply@v6-mail.com” for testing, only one autoreply message will be delivered within a minute.