Mailboxlayer for AI agents
Mailboxlayer is a REST API that validates and verifies email addresses to reduce bounces before a send, checking format and mail server availability. Connect it once through Arc0, and your agent, or Claude, ChatGPT and Cursor, can use it through one MCP endpoint, limited to what each user approved.
What agents do in Mailboxlayer.
Check validity, read-only
Validate a single email address for format and deliverability before adding it to a list, a read-only check with no side effects.
Screen a signup email
Check a newly submitted signup email for validity as part of a form workflow.
Verify a batch before import
Run a batch of addresses through validation before importing them into a mailing list.
1 Mailboxlayer actions, graded by risk.
Every Mailboxlayer action is tagged read, write or destructive, so one policy covers the whole app and new actions inherit the right default.
read
1Look things up. Allowed by default.
- mailboxlayer.check_emailCheck Email Validity
write
0Create and change things. Allow, or ask the user first.
- No write actions.
destructive
0Delete, cancel or archive. Ask first, or deny outright.
- No destructive actions.
Mailboxlayer in three steps.
- 01Your users connect MailboxlayerThey add their Mailboxlayer api key on Arc0 Connect, under your brand. It goes straight into the vault.
- 02You set the rulesReads run, and writes like “updates” can wait for the user to approve.
- 03Any agent can actYour agent calls Mailboxlayer through the Arc0 SDK or MCP, and so can Claude, ChatGPT and Cursor. Every call lands on the audit log.
await arc0.policies.set('mailboxlayer', { read: 'allow', write: 'ask', destructive: 'deny', }) # Claude Code: the same connection, one URL $ claude mcp add --transport http arc0 \ https://mcp.arc0.ai/u/u_8f2
How Mailboxlayer connects.
Users add their Mailboxlayer api key on Arc0 Connect. It is encrypted in the vault, never shown to the model, and each user can rotate or revoke it at any time.
The same Mailboxlayer connection serves your agent over MCP and your own backend over REST and the proxy, so a user connects once. How Arc0 handles credentials →
- AUTH
- API key
- CREDENTIALS
- Per-tenant encrypted vault
- MODEL SEES
- Results only, never credentials
- AUDIT LOG
- Every call, on every plan
Use Mailboxlayer from any agent.
ClaudeChatGPTCursor
Codex
VS CodeOpenAI Agents SDKClaude Agent SDK
Vercel AI SDK
Mastra
LangGraph
Mailboxlayer and Arc0, answered.
Can I use Mailboxlayer with Claude, ChatGPT or Cursor?
Yes. Connect Mailboxlayer to Arc0 once, then add your Arc0 MCP URL to Claude, ChatGPT, Cursor, Claude Code or any other remote-MCP client. Each assistant only gets the Mailboxlayer actions you allow.
How do users connect Mailboxlayer?
Users add their Mailboxlayer api key on Arc0 Connect. It is encrypted in the vault, never shown to the model, and each user can rotate or revoke it at any time.
Which Mailboxlayer actions can my agent take?
1 in total: 1 read, 0 write and 0 destructive. Your policies decide which of them each agent may call.
Can I make my agent read-only in Mailboxlayer?
Yes. Allow read actions and deny writes in the Mailboxlayer policy. Your agent can still look things up, and any write it attempts is blocked and logged.
Can my own backend call Mailboxlayer too?
Yes. The same Mailboxlayer connection is available over REST and through the Arc0 proxy, so your product and your agent share one connection per user.
Plug Mailboxlayer into your agent.
Your users connect Mailboxlayer once, under your brand. Your agent gets 1 actions behind your policies, with every call on the record.
Free to build · MCP + REST · Audit log on every plan