nice stack. one question from someone who just built one of these: how do you handle inbound email threading? in my case the provider (SES) rewrites the Message-ID in transit, so In-Reply-To/References matching silently breaks. I ended up putting the ticket id in a plus address on the Reply-To, the envelope survives even when the headers don't. also curious how you handle webhook redeliveries, for me duplicates turned out to be the normal case, not the rare one.