mail_app (Simple Mail App/ Just Mails)

A new Flutter project for myself. Learning and creating a mail app for windows (maybe translate to iOS in the maybe far future) which has all the features I need, nothing more and nothing less.

I started it because the mail clients I used got updated and reworked, in my opinion for the worse. This wil be a simple replacement for viewing and sending email without any bullshit features I do not need like calenders, planners, or proprietary folders.

In general I want support for multiple email addresses, options for showing unread at the top of the inbox, a shared inbox which combines the inboxes of all emails addresses, customization of the color pallet, and OAuth support for logging in.

Backend

The backend is written in Rust and uses a websocket to communicate with the frontend. It uses the imap crate to connect to the email servers. It stores a local cache of the emails in a sqlite database.

Run rust backend with cd backend && cargo run

Working Backend

• Login to IMAP server
• Logout from IMAP server
• Get logged in sessions
• Get messages sorted by time from local database
• Get messages with uids from local database
• Update local database from IMAP server
• Modify flags of messages
• Move messages between mailboxes
• Get mailboxes of session

Frontend

The frontend is written in Flutter and uses the web_socket_client package to communicate with the backend. The html emails are rendered with the flutter_widget_from_html package which converts html to flutter widgets.

Run flutter frontend with flutter run -d windows

Working Frontend

• Add IMAP account with username, password
• Switch mailboxes
• List emails in mailbox
• Scroll to load more emails
• View email html (some might not be 100% correct)
• View email text if no html
• Move to trash/all mail
• Mark as read/unread

Screenshots

Database Design

CONNECTIONS
username	PK	VARCHAR(500)
password		VARCHAR(500)
address	PK	VARCHAR(500)
port		INT
updated_at		DATETIME

MAILBOXES
connection_username	FK, PK	INT
connection_address	FK, PK	INT
path	PK	VARCHAR(500)
updated_at		DATETIME

MESSAGES
message_uid	PK	INT
connection_username	FK, PK	INT
connection_address	FK, PK	INT
mailbox_path	FK, PK	INT
session_id		INT
message_id		VARCHAR(500)
subject		VARCHAR(500)
from		VARCHAR(500)
sender		VARCHAR(500)
to		VARCHAR(500)
cc		VARCHAR(500)
bcc		VARCHAR(500)
reply_to		VARCHAR(500)
in_reply_to		VARCHAR(500)
delivered_to		VARCHAR(500)
date		DATETIME
received		DATETIME
html		TEXT
text		TEXT
updated_at		DATETIME

API spec

LOGIN

login to an IMAP server and create a session.

/login

• username (string): The username of the user
• password (string): The password of the user
• address (string): The address of the user
• port (int): The port of the user

{
    "success": true,
    "message": "message",
    "data": {                         // session id of new session
      "session_id": 1
    }
}

LOGOUT

Logout from the IMAP server and delete the session.

/logout

• session_id (int): The session id of the user

{
    "success": true,
    "message": "message"
}

GET_SESSIONS

Get all the logged in IMAP sessions

/get_sessions

{
    "success": true,
    "message": "message",
    "data": [                         // list of connected sessions
      {
        "session_id": 1,
        "username": "username",
        "address": "address",
        "port": 1
      }
    ]
}

GET_MAILBOXES

Get all the mailbox paths of a session.

/get_mailboxes

• session_id (int): The session id of the user

{
    "success": true,
    "message": "message",
    "data": [                         // list of mailbox paths
      "mailbox_path"
    ]
}

GET_MESSAGES_WITH_UIDS

Get a message from a mailbox using the message uids from the local database only.

/get_messages_with_uids

• session_id (int): The session id of the user
• mailbox_path (string): The mailbox path
• message_uids (comma separated list): The uids of the messages

{
  "success": true,
  "message": "message",
  "data": [                           // list of messages
    {
      "uid": 1,
      "sequence_id": 1,
      "message_id": "server message id",
      "subject": "subject",
      "from": [
        {
          "name": "Google",
          "mailbox": "no-reply",
          "host": "accounts.google.com"
        }
      ],
      "sender": [],                   // same object as from
      "to": [],                       // same object as from
      "cc": [],                       // same object as from
      "bcc": [],                      // same object as from
      "reply_to": [],                 // same object as from
      "in_reply_to": "email string",
      "delivered_to": "email string",
      "date": 1722093349000,
      "received": 1722093350000,
      "flags": ["Seen", "Flagged"],
      "html": "base64 encoded html",
      "text": "base64 encoded text"
    }
  ]
}

GET_MESSAGES_SORTED

get messages from a mailbox sorted on time with indexes
calculated from the start and end indexes of the index numbers.
Messages are retrieved from the local database only.

/get_messages_sorted

• session_id (int): The session id of the user
• mailbox_path (string): The mailbox path
• start (int): The start index of the messages
• end (int): The end index of the messages

{
  "success": true,
  "message": "message",
  "data": [                           // list of messages
    {
      "uid": 1,
      "sequence_id": 1,
      "message_id": "server message id",
      "subject": "subject",
      "from": [
        {
          "name": "Google",
          "mailbox": "no-reply",
          "host": "accounts.google.com"
        }
      ],
      "sender": [],                   // same object as from
      "to": [],                       // same object as from
      "cc": [],                       // same object as from
      "bcc": [],                      // same object as from
      "reply_to": [],                 // same object as from
      "in_reply_to": "email string",
      "delivered_to": "email string",
      "date": 1722093349000,
      "received": 1722093350000,
      "flags": ["Seen", "Flagged"],
      "html": "base64 encoded html",
      "text": "base64 encoded text"
    }
  ]
}

UPDATE_MAILBOX

Update the mailbox of a session from the IMAP server.\

Algorithm:

1. select command to get exists (total number of messages)

2. fetch message with sequence id exists to get the uid

3. check if message in local database with uid has the same sequence id

4. if not, message is moved/deleted/added in the mailbox

   • fetch 'UID' for 50 at the time until all sequence id and uid match
     • remove message uids present in the database but not in the fetched list
     • update sequence id of messages where the sequence id is different in the fetch
     • add message uids present in the fetched list but not in the database

5. always, fetch with 'FLAGS' of all messages in the mailbox to update flags

/update_mailbox

• session_id (int): The session id of the user
• mailbox_path (string): The mailbox path
• quick (bool?): will only fetch (20max) new messages and remove messages

{
  "success": true|false,
  "message": "message",
  "data": {
    "new_uids": [1, 2, 3],            // list of new uids
    "removed_uids": [1, 2, 3],        // list of removed uids (not in mailbox anymore)
    "changed_uids": [1, 2, 3],        // list of changed uids (flags changed)
  }
}

UPDATE_MAILBOXES

Update and get all the mailbox paths of a session from the IMAP server.

/update_mailboxes

• session_id (int): The session id of the user

{
    "success": true|false,
    "message": "message",
    "data": [                         // list of mailbox paths
      "INBOX",
      "mailbox_path"
    ]
}

MODIFY_FLAGS

Modify the flags of a message in a mailbox using the message uid.

/modify_flags

• session_id (int): The session id of the user
• mailbox_path (string): The mailbox path
• message_uid (int): The uid of the message
• flags (comma separated list): The flags to modify (e.g. "Seen,Flagged,Deleted")
• add (bool): If the flags should be added or removed

{
  "success": true,
  "message": "message",
  "data": [                           // list of all flags
    "Seen",
    "Flagged"
  ]
}

MOVE_MESSAGE

Move a message from one mailbox to another using the message uid.
The message will be copied to the destination mailbox and deleted from
the source mailbox using the IMAP move command.

/move_message

• session_id (int): The session id of the user
• message_uid (int): The uid of the message
• mailbox_path_dest (string): The destination mailbox path

{
  "success": true,
  "message": "message",
  "data": "mailbox_path_dest"         // destination mailbox path
}