Lightweight, asynchronous IMAP serving in Python.
Project description
pymap
Lightweight, asynchronous IMAP serving in Python.
This project attempts to simplify the complexity of the IMAP protocol into a set of clean Python APIs that can be implemented by pluggable backends. Everything runs in an asyncio event loop.
API Documentation
Docker Image
Table of Contents
Install and Usage
$ pip install pymap
$ pymap --help
$ pymap dict --help
$ pymap maildir --help
dict Plugin
The dict plugin uses in-memory dictionary objects to store mail and metadata. While the server is running, all concurrent and future connections will see the same data, including added and removed messages, but no changes will persist if the server is restarted.
You can try out the dict plugin with demo data:
$ pymap --port 1143 --debug dict --demo-data
In another terminal, connect to port 1143 and run some commands:
* OK [CAPABILITY IMAP4rev1 STARTTLS AUTH=PLAIN AUTH=LOGIN AUTH=CRAM-MD5 BINARY UIDPLUS MULTIAPPEND IDLE APPENDLIMIT=1000000000] Server ready my.hostname.local
. login demouser demopass
. OK Authentication successful.
. select INBOX
* OK [PERMANENTFLAGS (\Answered \Deleted \Draft \Flagged \Seen)] Flags permitted.
* FLAGS (\Answered \Deleted \Draft \Flagged \Recent \Seen)
* 4 EXISTS
* 1 RECENT
* OK [UIDNEXT 105] Predicted next UID.
* OK [UIDVALIDITY 4097774359] UIDs valid.
* OK [UNSEEN 4] First unseen message.
. OK [READ-WRITE] Selected mailbox.
. logout
* BYE Logging out.
. OK Logout successful.
Here are some other commands to try:
. uid fetch 1:* all
. list "" *
. create "A New Folder"
. store * +FLAGS (\Deleted)
. expunge
Add new messages using the append command:
. append INBOX (\Flagged) {38+}
From: user@example.com
test message!
maildir Plugin
The maildir plugin uses on-disk storage for mail and metadata. For mail data, it uses the eponymous Maildir format. However, since Maildir alone is not enough for modern IMAP usage, it is extended with additional data as described in Dovecot's MailboxFormat/Maildir, with the intention of being fully compatible.
For login, the plugin uses files compatible with the /etc/passwd,
/etc/shadow, and /etc/group formats. By default, they are
prefixed with pymap-etc- and placed inside the configured base directory to
avoid conflicting with the corresponding system files.
maildir Quick Start
Start the pymap server pointing to a base directory, e.g.:
$ pymap --port 1143 --debug maildir ~/maildir/
In another terminal, use pymap-admin to create a user to login with:
$ pymap-admin set-user demouser
# Type in a password at the prompt, e.g. "demopass"
If you already have a maildir folder that you could like to reuse, you can
re-assign your user's mailbox_path:
$ pymap-admin set-user --param mailbox_path=/path/to/mailbox demouser
# Re-type or change the password
You are now ready to login to IMAP on port 1143 using your favorite mail client.
redis Plugin
The redis plugin uses the Redis data structure store for mail and metadata. It requires redis-py and will not appear in the plugins list without it.
$ pip install 'pymap[redis]'
$ pymap redis --help
Keys are composed of a heirarchy of prefixes separated by /. For example, the
key containing the flags of a message might be:
/ns/eacb1cf1558741d0b5419b3f838882f5/mbx/Fdaddd3075d7b42e78a7edb1d87ee5800/msg/9173/flags
In this example, the eacb1cf1558741d0b5419b3f838882f5 and
Fdaddd3075d7b42e78a7edb1d87ee5800 prefixes are randomly generated IDs acting
as the namespaces for the login user and mailbox, respectively, and the message
has UID 9173.
redis Quick Start
Start the pymap server pointing to a local redis server, or use --address to
connect to a remote redis, e.g.:
$ pymap --port 1143 --debug redis # --address redis://my.redis
In another terminal, use pymap-admin to create a user to login with:
$ pymap-admin set-user demouser
# Type in a password at the prompt, e.g. "demopass"
You are now ready to login to IMAP on port 1143 using your favorite mail client.
Admin Tool
With optional dependencies, the pymap server will also open a gRPC service providing administrative operations for the running server.
$ pip install 'pymap[admin,macaroon]'
The admin service can create, update, and delete users, deliver new messages, check credentials, and provide health checks.
The pymap-admin CLI tool simplifies interacting with the admin service. It can also be installed standalone to interact with remote pymap servers:
$ pip install pymap-admin
$ pymap-admin --help
Configuring an MTA
The admin tool can be used as a "local delivery agent" for an MTA with
the append sub-command. For example, in postfix you might use:
mailbox_command = /some/where/pymap-admin --from "$SENDER" "$USER"
This setup may be combined with remote authentication to keep a clean separation between your MTA and pymap.
Supported Extensions
In addition to RFC 3501, pymap supports a number of IMAP extensions to give clients easier and more powerful use.
RFC 2177
Adds the IDLE capability and command, which lets clients wait (without
issuing commands) and receive mailbox updates as they happen without polling.
RFC 2180
Defines some conventions for handling multi-access in scenarios such as
EXPUNGE and mailbox deletion.
RFC 2971
Adds the ID capability and command, which lets clients send and receive
arbitrary information for "statistical" purposes and bug reports.
RFC 3502
Adds the MULTIAPPEND capability, allowing multiple messages to be atomically
appended to a mailbox with a single APPEND command.
RFC 3516
Adds the BINARY extension, providing better support for the encoding and
transfer of binary data.
RFC 4315
Adds the UIDPLUS capability, which adds the UID EXPUNGE command and defines
the APPENDUID and COPYUID giving clients more insight into the messages
added to a mailbox.
RFC 4466
No additional functionality by itself, but allows pymap to be extended easily and more robustly handle bad client implementations.
RFC 5530
Adds additional IMAP response codes that can help tell an IMAP client why a command failed.
RFC 7889 (partial)
Adds the APPENDLIMIT= capability, declaring the maximum message size a server
will accept from an APPEND command. Mailbox-specific limitations defined
by the RFC are not supported.
RFC 8474
Adds the OBJECTID capability, assigning unique IDs to mailboxes, messages,
and threads to improve client caching and display.
Development and Testing
You will need to do some additional setup to develop and test plugins. Install Hatch to use the CLI examples below.
Run all tests and linters:
$ hatch run check
Type Hinting
This project makes heavy use of Python's type hinting system, with the intention of a clean run of mypy.
No code contribution will be accepted unless it makes every effort to use type hinting to the extent possible and common in the rest of the codebase.
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