Advanced Usage

This document covers some more advanced features and tips for handling specific usages.

Cleaning Up Connections

To communicate with the server, IMAPClient establishes a TCP connection. It is important for long-lived processes to always close connections at some point to avoid leaking memory and file descriptors. This is usually done with the logout method:

import imapclient

c = imapclient.IMAPClient(host="")
c.login("", "passwd")

However if an error is raised when selecting the folder, the connection may be left open.

IMAPClient may be used as a context manager that automatically closes connections when they are not needed anymore:

import imapclient

with imapclient.IMAPClient(host="") as c:
    c.login("", "passwd")

Watching a mailbox using idle

The IDLE extension allows an IMAP server to notify a client when something changes in a mailbox. It can be used as an alternative to polling to receive new messages.

The concept is simple: the client connects to the server, selects a mailbox and enters the IDLE mode. At this point the server sends notifications whenever something happens in the selected mailbox until the client ends the IDLE mode by issuing a DONE command. This is explained in RFC 2177.

# Open a connection in IDLE mode and wait for notifications from the server

from imapclient import IMAPClient

HOST = ''
USERNAME = 'someuser'
PASSWORD = 'password'

server = IMAPClient(HOST)
server.login(USERNAME, PASSWORD)

# Start IDLE mode
print("Connection is now in IDLE mode, send yourself an email or quit with ^c")

while True:
        # Wait for up to 30 seconds for an IDLE response
        responses = server.idle_check(timeout=30)
        print("Server sent:", responses if responses else "nothing")
    except KeyboardInterrupt:

print("\nIDLE mode done")

Note that IMAPClient does not handle low-level socket errors that can happen when maintaining long-lived TCP connections. Users are advised to renew the IDLE command every 10 minutes to avoid the connection from being abruptly closed.

Handling large mailboxes


Interactive Sessions

When developing program using IMAPClient is it sometimes useful to have an interactive shell to play with. IMAPClient ships with a module that lets you fire up an interactive shell with an IMAPClient instance connected to an IMAP server.

Start a session like this:

python -m imapclient.interact -H <host> -u <user> ...

Various options are available to specify the IMAP server details. See the help (–help) for more details. You’ll be prompted for a username and password if one isn’t provided on the command line.

It is also possible to pass connection details as a configuration file like this:

python -m imapclient.interact -f <config file>

See below for details of the configuration file format.

If installed, IPython will be used as the embedded shell. Otherwise the basic built-in Python shell will be used.

The connected IMAPClient instance is available as the variable “c”. Here’s an example session:

$ python -m imapclient.interact -H <host> -u <user> ...

IMAPClient instance is "c"
In [1]: c.select_folder('inbox')
{b'EXISTS': 2,
 b'FLAGS': (b'\\Answered',
 b'PERMANENTFLAGS': (b'\\Answered',
 b'READ-WRITE': True,
 b'RECENT': 0,
 b'UIDNEXT': 1339,
 b'UIDVALIDITY': 1239278212}

In [2]:
Out[2]: [1123, 1233]

In [3]: c.logout()
Out[3]: b'Logging out'

Configuration File Format

Both the IMAPClient interactive shell and the live tests take configuration files which specify how to to connect to an IMAP server. The configuration file format is the same for both.

Configuration files use the INI format and must always have a section called DEFAULT. Here’s a simple example:

host =
username = bob
password = sekret
ssl = True

The supported options are:

Name Type Description
host string IMAP hostname to connect to.
username string The username to authenticate as.
password string The password to use with username.
port int Server port to connect to. Defaults to 143 unless ssl is True.
ssl bool Use SSL/TLS to connect.
starttls bool Use STARTTLS to connect.
ssl_check_hostname bool If true and SSL is in use, check that certificate matches the hostname (defaults to true)
ssl_verify_cert bool If true and SSL is in use, check that the certifcate is valid (defaults to true).
ssl_ca_file string If SSL is true, use this to specify certificate authority certs to validate with.
timeout int Time out I/O operations after this many seconds.
oauth2 bool If true, use OAUTH2 to authenticate (username and password are ignored).
oauth2_client_id string OAUTH2 client id.
oauth2_client_secret string OAUTH2 client secret.
oauth2_refresh_token string OAUTH2 token for refreshing the secret.

Acceptable boolean values are “1”, “yes”, “true”, and “on”, for true; and “0”, “no”, “false”, and “off”, for false.

Thread Safety

Instances of IMAPClient are NOT thread safe. They should not be shared and accessed concurrently from multiple threads.