The one I know of with this feature is Haven by nostr:nprofile1qqsw9n8heusyq0el9f99tveg7r0rhcu9tznatuekxt764m78ymqu36cpr3mhxue69uhhyetvv9ujucnfw33k76twwpshy6ewvdhk6tcpzdmhxue69uhhwmm59e6hg7r09ehkuef0qy2hwumn8ghj7un9d3shjtn4w3ux7tn0dejj7ne6u4e.

Here's the repo:

https://github.com/bitvora/haven

Great relay that is really 4 relays in 1, plus a Blossom server for self-hosting your media.

Any other relay that blasts your posts to other relays would probably describe that feature on their GitHub readme. I remember the guys at Mutiny Wallet built a blastr relay a while ago, too.

You really don't need to blast your notes out to a bunch of relays, though. Especially as more and more Nostr apps hopefully adopt the outbox model.