I don't know enough to say for sure, but as far as I can tell servers can't see your messages or metadata even if they tried, that said I only use servers from other Nostriches, nostr:npub1y3uh89v5a4vq92t8q0j6su94zhvcdxpywjn3l6hpsr5welarqtrqj7yzhd runs one too which I use