Trigger script upon email receipt
I need to trigger a python script every time an email is received by my webserver on a specific account. I will also need the email to be passed to the script as an argument. My webserver is using Dovecot. How do I go about doing this?
Answer
I recommend you have a look at Twisted and specifically its IMAP and POP protocols and client modules.
As an example:
#!/usr/bin/env python
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Simple IMAP4 client which displays the subjects of all messages in a
particular mailbox.
"""
import sys
from twisted.internet import protocol
from twisted.internet import ssl
from twisted.internet import defer
from twisted.internet import stdio
from twisted.mail import imap4
from twisted.protocols import basic
from twisted.python import util
from twisted.python import log
class TrivialPrompter(basic.LineReceiver):
from os import linesep as delimiter
promptDeferred = None
def prompt(self, msg):
assert self.promptDeferred is None
self.display(msg)
self.promptDeferred = defer.Deferred()
return self.promptDeferred
def display(self, msg):
self.transport.write(msg)
def lineReceived(self, line):
if self.promptDeferred is None:
return
d, self.promptDeferred = self.promptDeferred, None
d.callback(line)
class SimpleIMAP4Client(imap4.IMAP4Client):
"""
A client with callbacks for greeting messages from an IMAP server.
"""
greetDeferred = None
def serverGreeting(self, caps):
self.serverCapabilities = caps
if self.greetDeferred is not None:
d, self.greetDeferred = self.greetDeferred, None
d.callback(self)
class SimpleIMAP4ClientFactory(protocol.ClientFactory):
usedUp = False
protocol = SimpleIMAP4Client
def __init__(self, username, onConn):
self.ctx = ssl.ClientContextFactory()
self.username = username
self.onConn = onConn
def buildProtocol(self, addr):
"""
Initiate the protocol instance. Since we are building a simple IMAP
client, we don't bother checking what capabilities the server has. We
just add all the authenticators twisted.mail has. Note: Gmail no
longer uses any of the methods below, it's been using XOAUTH since
2010.
"""
assert not self.usedUp
self.usedUp = True
p = self.protocol(self.ctx)
p.factory = self
p.greetDeferred = self.onConn
p.registerAuthenticator(imap4.PLAINAuthenticator(self.username))
p.registerAuthenticator(imap4.LOGINAuthenticator(self.username))
p.registerAuthenticator(
imap4.CramMD5ClientAuthenticator(self.username))
return p
def clientConnectionFailed(self, connector, reason):
d, self.onConn = self.onConn, None
d.errback(reason)
def cbServerGreeting(proto, username, password):
"""
Initial callback - invoked after the server sends us its greet message.
"""
# Hook up stdio
tp = TrivialPrompter()
stdio.StandardIO(tp)
# And make it easily accessible
proto.prompt = tp.prompt
proto.display = tp.display
# Try to authenticate securely
return proto.authenticate(password
).addCallback(cbAuthentication, proto
).addErrback(ebAuthentication, proto, username, password
)
def ebConnection(reason):
"""
Fallback error-handler. If anything goes wrong, log it and quit.
"""
log.startLogging(sys.stdout)
log.err(reason)
return reason
def cbAuthentication(result, proto):
"""
Callback after authentication has succeeded.
Lists a bunch of mailboxes.
"""
return proto.list("", "*"
).addCallback(cbMailboxList, proto
)
def ebAuthentication(failure, proto, username, password):
"""
Errback invoked when authentication fails.
If it failed because no SASL mechanisms match, offer the user the choice
of logging in insecurely.
If you are trying to connect to your Gmail account, you will be here!
"""
failure.trap(imap4.NoSupportedAuthentication)
return proto.prompt(
"No secure authentication available. Login insecurely? (y/N) "
).addCallback(cbInsecureLogin, proto, username, password
)
def cbInsecureLogin(result, proto, username, password):
"""
Callback for "insecure-login" prompt.
"""
if result.lower() == "y":
# If they said yes, do it.
return proto.login(username, password
).addCallback(cbAuthentication, proto
)
return defer.fail(Exception("Login failed for security reasons."))
def cbMailboxList(result, proto):
"""
Callback invoked when a list of mailboxes has been retrieved.
"""
result = [e[2] for e in result]
s = '\n'.join(['%d. %s' % (n + 1, m) for (n, m) in zip(range(len(result)), result)])
if not s:
return defer.fail(Exception("No mailboxes exist on server!"))
return proto.prompt(s + "\nWhich mailbox? [1] "
).addCallback(cbPickMailbox, proto, result
)
def cbPickMailbox(result, proto, mboxes):
"""
When the user selects a mailbox, "examine" it.
"""
mbox = mboxes[int(result or '1') - 1]
return proto.examine(mbox
).addCallback(cbExamineMbox, proto
)
def cbExamineMbox(result, proto):
"""
Callback invoked when examine command completes.
Retrieve the subject header of every message in the mailbox.
"""
return proto.fetchSpecific('1:*',
headerType='HEADER.FIELDS',
headerArgs=['SUBJECT'],
).addCallback(cbFetch, proto
)
def cbFetch(result, proto):
"""
Finally, display headers.
"""
if result:
keys = result.keys()
keys.sort()
for k in keys:
proto.display('%s %s' % (k, result[k][0][2]))
else:
print "Hey, an empty mailbox!"
return proto.logout()
def cbClose(result):
"""
Close the connection when we finish everything.
"""
from twisted.internet import reactor
reactor.stop()
def main():
hostname = raw_input('IMAP4 Server Hostname: ')
port = raw_input('IMAP4 Server Port (the default is 143, 993 uses SSL): ')
username = raw_input('IMAP4 Username: ')
password = util.getPassword('IMAP4 Password: ')
onConn = defer.Deferred(
).addCallback(cbServerGreeting, username, password
).addErrback(ebConnection
).addBoth(cbClose)
factory = SimpleIMAP4ClientFactory(username, onConn)
from twisted.internet import reactor
if port == '993':
reactor.connectSSL(hostname, int(port), factory, ssl.ClientContextFactory())
else:
if not port:
port = 143
reactor.connectTCP(hostname, int(port), factory)
reactor.run()
if __name__ == '__main__':
main()
From here you need to just call your Python script in a subprocess when you detect a new email from your IMAP folder that you're checking... Here you could also use Twisted's Process handling as documented here: https://twistedmatrix.com/documents/13.0.0/core/howto/process.html
Good luck!