Connect OCN Mail to Claude,
Cursor, ChatGPT, any MCP client
Give your AI agent a real ocn.ne.jp inbox. Read, search, send, reply, schedule and organize mail over IMAP, using the mail password NTT issues for OCN mail rather than the one that connects you to the internet.
Claude cannot reach OCN mail on its own. MCPEmails is a hosted MCP server that connects it over IMAP at imap.ocn.ne.jp on port 993, authenticating with your full OCN address and the OCN メールパスワード, so Claude, Cursor or any MCP client can read, search, send and organize that mail. The credential is the part people get wrong: NTT keeps a separate connection password for the OCN line and a separate mail password for the mailbox, and only the mail password works here. There is no app password and no switch to flip. One inbox is free, forever.
How OCN connects: IMAP over SSL, and the mail password from your membership certificate
NTT documents OCN mail at imap.ocn.ne.jp on port 993 with SSL for incoming mail, and smtp.ocn.ne.jp on port 465 with SSL and authentication for outgoing. The username on both is the complete address. The password is the メールパスワード, a 6 to 32 character string printed on the OCN membership certificate (OCN会員登録証) and used for both mail software and the OCN webmail. NTT says plainly that it is separate from the connection password (接続用パスワード, also called the 認証パスワード) that authenticates the OCN line itself, and that the server values printed on an older certificate may be out of date, so the hosts on this page come from NTT's current support page rather than from the paper. Autodiscovery does not help with OCN: the public Mozilla database lists only POP for ocn.ne.jp, which is why a mail client that fills in settings for you may offer no IMAP at all.
The exact OCN IMAP and SMTP settings
Copy these into the connect form. MCPEmails prefills them where it can, and retries the other standard transport if the first does not answer.
| Protocol | Server | Port | Security |
|---|---|---|---|
| IMAP (incoming) | imap.ocn.ne.jp | 993 | TLS (implicit) |
| SMTP (outgoing) | smtp.ocn.ne.jp | 465 | TLS (implicit) |
Verified 2026-11-04: imap.ocn.ne.jp answered a TLS connection and identified itself as an IMAP server under that name. It advertises LOGIN, PLAIN authentication.
Sign in with: Your full OCN address, name@ocn.ne.jp, entered in full. NTT's guide says explicitly to type the whole address, not the part before the @.
An OCN inbox your agent can actually use
21 action-based MCP tools: send, reply, forward, schedule, and organize. Your agent finishes the job inside OCN.
- 01Read
Read & search mail
List, read and search across folders to find that invoice, summarize a thread, or pull the latest from a sender.
- 02Send
Send, reply & forward
Compose and send real messages, reply in-thread, and forward, directly from your mailbox, not as a draft you finish by hand.
- 03Schedule
Schedule for later
Queue a message to go out at the right time, so your agent can draft now and send on schedule.
- 04Organize
Move, copy, flag, archive, delete
Keep the inbox tidy: file mail into folders, flag what matters, archive the rest, or delete on request.
Connect OCN in four steps
From sign-up to first AI email in a couple of minutes.
Create your free MCPEmails account
Sign up at mcpemails.com. The free plan connects one inbox forever and asks for no card.
Find your OCN mail password
It is the value in the メールパスワード field of your OCN membership certificate, the document NTT sent when the line was set up. It is not the connection password printed next to it. If you no longer have the certificate or the password has been changed, set a new mail password through your OCN account settings, then use the new value.
Enter the full address and the mail password in MCPEmails
Choose IMAP / SMTP, enter the complete address such as name@ocn.ne.jp, and paste the mail password. The OCN hosts and ports are prefilled and were confirmed from a live TLS connection.
Paste the MCP URL into your AI client
Drop https://mcpemails.com/api/mcp into Claude, Cursor or ChatGPT, authorize, and your agent can read, search, send, reply, forward, schedule and organize the OCN mailbox.
Step-by-step guides: How to connect Claude to your email · Claude IMAP connector guide
More guides: Inbox zero with AI · Give your AI agent an inbox
Use this inbox in your AI app: Claude · ChatGPT · Cursor · VS Code · Codex · Claude Code · Cline · Windsurf · Gemini CLI · All supported apps
Need the server names and ports? Look up IMAP and SMTP settings
Comparing providers first? See the email provider compatibility matrix
Use OCN in ChatGPT
ChatGPT reaches OCN through a custom MCP server, which you add on chatgpt.com with ChatGPT Go or a paid plan.
- Connect OCN to MCPEmails with the steps above.
- On chatgpt.com, open Plugins, Personal, click Add, then Add custom MCP server.
- Name it MCPEmails, paste
https://mcpemails.com/api/mcpunder Connection, choose OAuth, confirm, click Create as a plugin and sign in to MCPEmails. - In a chat, type @ and pick MCPEmails. Do it again when a follow-up needs your mail.
What actually goes wrong with OCN
Two passwords on one account, and the mail server takes only one
An OCN subscription comes with a connection password that signs the line onto the network and a mail password that opens the mailbox. NTT documents them as separate things and the mail server honours only the second. Entering the connection password, or the password for the OCN customer portal, produces an ordinary authentication failure with nothing in it to explain which credential was wrong. If a correct-looking password is refused, check which of the two you pasted before changing anything else.
The address goes in whole, not the part before the @
NTT's guide tells you to enter the entire mail address as the username on both the incoming and the outgoing server. Several Japanese providers take only the local part, and clients that copy settings from one ISP to another tend to carry that habit over. On OCN a username of name alone, or name@ocn, fails in the same way a wrong password would. MCPEmails sends the full address.
Outgoing mail is capped at 10 MB
smtp.ocn.ne.jp announces a maximum message size of 10,485,760 bytes, which is the lowest of any provider on this site. That ceiling is on the whole encoded message, so a base64 attachment counts about a third larger than its size on disk; an attachment of roughly 7 MB is already at the limit. An agent asked to forward something bigger gets a hard rejection at send time. Share a link instead.
No MOVE and no SPECIAL-USE, so folders are matched by name
When probed, imap.ocn.ne.jp advertised IDLE but neither MOVE, UIDPLUS nor SPECIAL-USE. Filing a message runs as a copy, a flag update and an expunge rather than one command, and the sent, drafts and trash folders are found by their names rather than by a role the server declares. If an agent cannot find a folder, name it in the instruction.
Known limits with OCN
- The SMTP server accepts messages up to 10 MB. Larger forwards are refused rather than queued, so attach a link instead of a large file.
- Because the server does not advertise MOVE, a move is not atomic. If a connection drops mid-operation a message can briefly exist in both folders.
- There is no app password and no OAuth path, so the stored credential is your OCN mail password. Changing it disconnects the mailbox until you enter the new one.
OCN and AI: common questions
Does Claude work with OCN mail?
Not on its own. Claude has no built-in OCN connector and cannot open an IMAP connection by itself. Connecting an MCP server such as MCPEmails to the mailbox over IMAP gives Claude read, search, send, reply, forward, schedule and organize access to it, and the same connection works from Cursor, ChatGPT and other MCP clients.
What are the OCN IMAP and SMTP settings?
IMAP is imap.ocn.ne.jp on port 993 with SSL. SMTP is smtp.ocn.ne.jp on port 465 with SSL and authentication. The username is your full OCN address, and the password is the OCN mail password. Both hosts were confirmed from a live TLS connection on the date shown on this page.
Which OCN password do I use for a mail app?
The メールパスワード, the mail password printed in its own field on the OCN membership certificate and used for the OCN webmail. NTT documents it as separate from the connection password that authenticates the line. If you do not have it, set a new mail password through your OCN account settings.
Why does my mail client offer only POP for OCN?
Because the public autoconfiguration database that many clients consult lists only POP3 for ocn.ne.jp. IMAP exists and is documented by NTT; you just have to enter imap.ocn.ne.jp, port 993 and SSL by hand. MCPEmails prefills those values.
Does OCN need an app password?
No. OCN has no app-specific password scheme and no per-client credential. The OCN mail password authenticates both IMAP and SMTP.
Is my OCN mail stored on your servers?
No. Messages are fetched live from OCN over IMAP for each request and passed to your AI client. Credentials are encrypted at rest and message bodies are not retained.
Can ChatGPT read my OCN mail?
Yes, once OCN is connected to MCPEmails. On chatgpt.com, add a custom MCP server with the URL https://mcpemails.com/api/mcp and OAuth sign-in. That works with ChatGPT Go and paid plans. ChatGPT gets only the access you approve, and your mail is fetched live, never stored.
Give your AI an OCN inbox
Connect OCN mail in minutes with the mail password. One inbox free forever, no card required.