I'm an idiot
If you sent me any email in the past 3 days, please resend it.
I messed up my server config and ended up black-holing all mail to two of my domains, no bounce messages, just gone.
Commence making fun of me................ now!
Running qmail on a Slackware host. In order to use virtual domain hosting in a manner that made more sense from an administrative standpoint, I configured the main server hostname as an unused domain. In an effort to save money, I decided to let that unused domain expire, and therefore replaced it in the qmail configs with an active domain, causing a conflict with the virtual setup. Since the virt mapping are ignored entirely for "local" domains, everything sent inbound for that domain was to a non-existent user. qmail doesn't validate recipients before accepting an inbound message, it rather chooses to bounce later (why, IDK. stupidest decision ever in what is otherwise the greatest MTA of all time). This behavior causes qmail to send unsolicited bounces, which gets you blacklisted and generally turn you into a spammer asshole in this day & age. Because of this, I chose to blackhole all mail for local & virtual domains destined for non-existent user accounts. (I know, I know, but it beats being blacklisted all the time, and my colo provider threatening to unplug me). I justify this choice by having a blatant warning display in my SMTP session headers, not than anybody ever reads those, but hey - it helps me sleep at night ;-)