AgentMail vs Nylas vs Ujex Postbox
AgentMail: agent-native, easiest start, paid above free tier, vendor-managed.
Nylas: connects agent to existing Gmail/Outlook/etc via OAuth.
Ujex Postbox: self-hostable, Apache-2.0, agent-native API + prompt-injection score + mobile approval.
What each one is
- AgentMail — a hosted, API-first email provider designed for agents from day one. You call
POST /inboxesand get a fresh address. Inbound is delivered via webhook. Out-of-the-box DKIM/SPF/DMARC. YC, $6M seed in March 2026. - Nylas — a unified API across Gmail, Outlook, Exchange, Yahoo, iCloud, IMAP. The agent connects to a human's inbox via OAuth. Different shape — your agent acts as a person logged into their own mail.
- Ujex Postbox — open-source (Apache-2.0 SDK) agent email infrastructure. Self-hostable. Same agent-native shape as AgentMail, plus prompt-injection scoring, mobile approve-before-send, and integration with the rest of Ujex (memory, audit, budgets, ingress).
Capability matrix
| AgentMail | Nylas | Ujex Postbox | |
|---|---|---|---|
| Per-agent inbox via API | ✓ | ✗ | ✓ |
| Connect to existing Gmail/Outlook | ✗ | ✓ (six providers) | ✗ |
| Inbound webhook | ✓ | ✓ | ✓ |
| Outbound with DKIM/SPF/DMARC | ✓ | ✓ (provider's keys) | ✓ (your keys) |
| Prompt-injection scoring | Some | ✗ | ✓ (heuristic + Gemini) |
| Mobile approve-before-send | ✗ | ✗ | ✓ (FCM push) |
| Self-hostable | ✗ | ✗ | ✓ |
| Apache-2.0 SDK | ✗ | ✗ | ✓ |
| MCP server | ✓ | ✓ | ✓ |
| Same auth as memory + audit + budgets | n/a (separate vendor) | n/a | ✓ (Ujex platform) |
| Free tier | Yes (limited) | Yes (limited) | Yes (1 inbox · 50/day) |
Pick AgentMail if
- You want the polished, vendor-managed path
- You don't want to operate any mail infrastructure
- You're scaling to 100+ inboxes and willing to pay
- You don't need cross-product integration (memory + audit + ingress in one stack)
Pick Nylas if
- The agent uses a human's existing inbox (Gmail, Outlook, etc.)
- You want one API across multiple providers
- OAuth flow is acceptable
Pick Ujex Postbox if
- You want self-hostable, Apache-2.0 SDK
- Prompt-injection scoring is part of your threat model
- You want mobile approve-before-send out of the box
- You're already on Ujex for memory / audit / budgets / ingress (same Firebase project)
What about combining?
You can use Nylas for the "connect to user's Gmail" agent and Ujex Postbox for the "agent's own inbox" agent within the same product. Different addresses, different code paths, both fine.
FAQ
Can I migrate from AgentMail to Ujex?
Yes — switch your domain's MX records, recreate inboxes via Ujex API, optionally route old addresses through Postbox during migration. AgentMail and Ujex addresses can coexist on different domains indefinitely.
Does Ujex Postbox have the same deliverability as AgentMail?
When self-hosted with proper DKIM/SPF/DMARC and a warmed IP, yes. AgentMail does the IP warming for you. For low-volume new domains, both have first-week-deliverability bumps.