I've had an Antec P180 getting dusty for about 7 years since the motherboard inside it died and I wasn't really using it much. The P180 and related models were designed in collaboration with the founder of https://silentpcreview.com/
In my first post-uni job I built a mailserver to sit in the IT team's office of a firm of solicitors. Used a Fractal Define R2 case and a Scythe Ninja cooler, with the fans that came with the case and cooler. This was about a decade ago, so the Define series is up to 7 now, and there have been a few generations of Ninja, but I expect you could put pretty much anything in there and have it somewhere between silent and quiet. The Define's panels had a heavy rubbery layer on the inside, with flaps to leave in place over fan positions that weren't used. The bays for 3.5" drives were soft-mounted.
I've had an Antec P180 getting dusty for about 7 years since the motherboard inside it died and I wasn't really using it much. The P180 and related models were designed in collaboration with the founder of https://silentpcreview.com/
In my first post-uni job I built a mailserver to sit in the IT team's office of a firm of solicitors. Used a Fractal Define R2 case and a Scythe Ninja cooler, with the fans that came with the case and cooler. This was about a decade ago, so the Define series is up to 7 now, and there have been a few generations of Ninja, but I expect you could put pretty much anything in there and have it somewhere between silent and quiet. The Define's panels had a heavy rubbery layer on the inside, with flaps to leave in place over fan positions that weren't used. The bays for 3.5" drives were soft-mounted.
Price varies according to size and generation, but always good VFM.
https://www.scan.co.uk/search?q=define