title: FastMail Sieve Extensions and Advent Calendar tags: Security date: 2017-12-13 09:26:00 I always enjoy the annual FastMail advent calendar blog posts. This week the [published an article](https://blog.fastmail.com/2017/12/12/more-sieve-extensions/) detailing some of the ways that sieve extensions are exposed to FastMail users. [Follow along](https://blog.fastmail.com/2017/12/01/fastmail-advent-2017/) for the rest of the holiday season. You might find out about features you're missing out on.