NTT Docomo

docomo Mail IMAP Interface

The docomo Mail IMAP interface is the one machine-interface specification NTT DOCOMO publishes openly, without registration, to third-party developers. It documents how a mail client connects to the docomo Mail service over IMAP, and is distributed as a 96-page Japanese PDF specification (mail_imap_spec_260126.pdf, HTTP 200, application/pdf, 1,229,737 bytes, edition 4.5 dated 2026-01-26, first edition 2013-12-19). This is an IMAP protocol interface, not an HTTP API: there is no REST surface, no OpenAPI definition, no API key issuance and no sandbox associated with it. The specification is complete and unredacted — it names the two production endpoints (imap.spmode.ne.jp and imap2.spmode.ne.jp, both on port 993), pins TLS 1.2 with an explicit allow-list of ten cipher suites and a 2048-bit public key, authenticates with d ACCOUNT ID and password, and specifies 31 IMAP commands including IDLE, NAMESPACE, UID EXPUNGE and the QUOTA family. The imap2 endpoint exists for the standard iPhone/iPad mailer and deliberately differs in behaviour, rewriting multipart structure for Deco-mail pictures and transcoding i-mode pictographs to Unicode emoji.

Documentation GitHub

Documentation

📖

Documentation

https://www.docomo.ne.jp/service/developer/smart_phone/application/imap/

📖

APIReference

https://www.docomo.ne.jp/binary/pdf/service/developer/smart_phone/application/imap/mail_imap_spec_260126.pdf

Other Resources

🔗

Conventions

https://raw.githubusercontent.com/api-evangelist/ntt-docomo/refs/heads/main/conventions/ntt-docomo-conventions.yml

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API entry from apis.yml

aid: ntt-docomo:docomo-mail-imap-interface
name: docomo Mail IMAP Interface
description: 'The docomo Mail IMAP interface is the one machine-interface specification NTT DOCOMO publishes
  openly, without registration, to third-party developers. It documents how a mail client connects to
  the docomo Mail service over IMAP, and is distributed as a 96-page Japanese PDF specification (mail_imap_spec_260126.pdf,
  HTTP 200, application/pdf, 1,229,737 bytes, edition 4.5 dated 2026-01-26, first edition 2013-12-19).
  This is an IMAP protocol interface, not an HTTP API: there is no REST surface, no OpenAPI definition,
  no API key issuance and no sandbox associated with it. The specification is complete and unredacted
  — it names the two production endpoints (imap.spmode.ne.jp and imap2.spmode.ne.jp, both on port 993),
  pins TLS 1.2 with an explicit allow-list of ten cipher suites and a 2048-bit public key, authenticates
  with d ACCOUNT ID and password, and specifies 31 IMAP commands including IDLE, NAMESPACE, UID EXPUNGE
  and the QUOTA family. The imap2 endpoint exists for the standard iPhone/iPad mailer and deliberately
  differs in behaviour, rewriting multipart structure for Deco-mail pictures and transcoding i-mode pictographs
  to Unicode emoji.'
humanURL: https://www.docomo.ne.jp/service/developer/smart_phone/application/imap/
baseURL: imaps://imap.spmode.ne.jp:993
tags:
- Email
- IMAP
- Protocol
- Specification
properties:
- type: Documentation
  url: https://www.docomo.ne.jp/service/developer/smart_phone/application/imap/
- type: APIReference
  url: https://www.docomo.ne.jp/binary/pdf/service/developer/smart_phone/application/imap/mail_imap_spec_260126.pdf
- type: Conventions
  url: conventions/ntt-docomo-conventions.yml