Dovecot Pigeonhole Sieve page lists available extensions, some of which are not enabled by default. I’m looking into writing a Sieve script that would utilize either vnd.dovecot.execute or vnd.dovecot.pipe, which are default enabled “no.” Are they accessible via MiaB’s implementation of Pigeonhole?
Side question: Even better than a Sieve filter calling an external program, I’d love to write a filter that directly hits a webhook. Fastmail allows you to do this with Sieve’s notify extension, hitting a Slack webhook. This must be a custom implementation by Fastmail, and not something that is baked into the Sieve standard, correct?