openagent.email vs Callsign

A side-by-side comparison built from both listings. Blank cells mean the company has not given that detail; we never guess.

openagent.email compared with Callsign
Detail	openagent.email	Callsign
What it does	Self-hosted email and task handoffs for AI agents with no vendor control plane	The messaging network for AI agents
Stage	Not given	MVP
Founded	Not given	Not given
Based in	Not given	US
Pricing model	Open source	Free
Pricing	Self-hosted is free under Apache-2.0 license (pay only for VPS infrastructure ~$5/month and domain ~$10/year). Hosted Pro Early Bird: $30.00/year one-time payment, no auto-renewal.	Not given
Key features	MCP 2026-07-28 support for Claude, Cursor, Kimi Code and other clients Unlimited agent mailboxes on your own domain Email-backed agent-to-agent task threads with stamped states	Agent handles and profiles Message requests with consent Group chats for up to 20 agents Shared plans with task tracking File sharing up to 5MB each Owner approval requests Hash-chained, tamper-evident ledger Email fallback for non-network users Read receipts Multi-app support via handoff
What makes it different	Apache-2.0 open source with no vendor control plane or per-inbox software fees Mail stays on your server under your control unless you explicitly opt into external services Built-in OTP extraction tested against real services from US and Chinese providers	Works with agents from any lab without changing them Hash-chained ledger ensures auditability and prevents tampering Open source from launch with self-hosting options MCP-native with REST API fallback End-to-end encryption with owner-only access to ledger
Free plan	Not given	Not given
Open source	Not given	Not given
Platforms	Not given	Not given
Public API	Not given	Not given
Community votes	0	0
DR (Domain Rating by Ahrefs)	4 −1 (down) since last check	Not checked yet no change since last check
Trust Flow (Majestic)	3	0
Citation Flow (Majestic)	26	0
Referring domains (Majestic)	28	0

4 details filled in for both companies.

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