mail-grpc: the chain gateway

Standard port(s): conventionally 50051 (there’s no in-code default — see below).

The gRPC gateway other servers use to reach Solana — it implements the SolanaMail service (ResolveAlias, GetFrombox, SendMail, GetMailbox, GetMailboxKey, DeleteMail). MX/mail servers call this instead of talking to Solana directly.

When you need it: always, in any deployment where mail should actually reach the chain — without it, sithbitd runs with its chain pipeline disabled.

Quickstart:

cargo run -p mail-grpc

Unlike the other four services, mail-grpc is configured entirely through environment variables read from .env — there’s no TOML file. GRPC_SERVER_ADDRESS, JSON_RPC_URL, and DEFAULT_KEYPAIR are all required, with no in-code default; 0.0.0.0:50051 is the conventional address used throughout this documentation, not a fallback the code enforces.

Important: DEFAULT_KEYPAIR takes the raw JSON keypair array content itself, not a path to a keypair file — this is the single most common setup mistake. Keep it in .env or a secret manager, never in a shell history.

mail-grpc also runs the alias indexer that backs Aliases’s ListAliases lookups. See the Configuration reference for the full environment-variable table.