ReallySimpleEmail

A deliberately minimal, read-only IMAP client for iOS. No dependencies - the IMAP client is ~240 lines of Network.framework on top of TLS.

What it does

• One or more IMAP accounts (implicit TLS, usually port 993).
• First sync of an account pulls the last 30 days; every sync after that keeps that same start date, so nothing you have already synced disappears.
• Messages are stored locally (SwiftData) with their plain text body, so reading works offline.
• Seen state is local only. Swipe a row either direction to toggle it.

What it deliberately cannot do

There is no code path that writes to a mail server:

• IMAPConnection.execute(_:) checks every command against an allowlist (CAPABILITY, NOOP, LOGIN, LOGOUT, EXAMINE, LIST, STATUS, SEARCH, FETCH, ID, plus UID SEARCH / UID FETCH). Anything else throws before a byte is sent.
• Mailboxes are opened with EXAMINE, not SELECT - the server itself grants the session no write permission.
• Bodies are fetched with BODY.PEEK[], which does not set \Seen.

So the server never learns what you read, and nothing can be deleted, moved or flagged from this app.

Layout

Mail/
  IMAPConnection.swift  TLS socket, tagged commands, literal-aware reader, allowlist
  IMAPClient.swift      login / examine / uid search / uid fetch, envelope parsing
  IMAPParser.swift      tokeniser for atoms, quoted strings, NIL, nested lists
  MIME.swift            RFC 2047 headers, quoted-printable, base64, charsets, multipart
  MailSync.swift        drives a sync into SwiftData
  Keychain.swift        passwords (never stored in the database)
Models/                 MailAccount, MailMessage
Views/                  mailbox list, message detail, account management

Notes / limits

• TLS on connect only; no STARTTLS on port 143, no OAuth.
• Only the first 64 KB of a message is downloaded (MailSync.maxBodyBytes); attachments are ignored, HTML is flattened to text.
• Sync is manual: pull to refresh, or the toolbar button.

App icon

Tools/GenerateAppIcon.swift draws the icon (a little envelope with a face) with CoreGraphics and writes the light, dark and tinted 1024x1024 PNGs straight into the asset catalog:

xcrun swift Tools/GenerateAppIcon.swift ReallySimpleEmail/Assets.xcassets/AppIcon.appiconset