The other day I had two different clients asking about processing e-mail from a python program. In particular, each e-mail message that comes in gets handed off to be processed by this program. Setting up the mail server to call the program is fairly easy, by configuring local delivery and using the .forward file or similar. However, the program which processes the message needs to do a number of things to do it's job reliably.

I pulled together some pieces of existing code I had to handle these issues. Read on for an example of my code for processing e-mail.

The main responsibilities that need to be handled are:

• Report if a Traceback happens.
• Give the system administrator the opportunity to correct Tracebacks and re-process the message before bouncing it.
• Log errors and tracebacks.
• Parse the incoming message.
• Report success when the message is completely processed.

This sample includes the ability to report tracebacks via syslog directly, by providing information back to the mail server (via stderr, which many mail servers honor), and by e-mailing a traceback report.

Below is the code I came up with, the highlighted portion is where the custom processing would be done.

This source can be downloaded from the ftp.tummy.com FTP site under /pub/tummy/pythonmailrcpt. This code is placed in the public domain, feel free to use it.

Mail processing example:

1. !/usr/bin/env python

3. &nbsp_place_holder;Python program which receives e-mail.

4. &nbsp_place_holder;

5. import rfc822, syslog, sys, random, os

6. &nbsp_place_holder;

7. &nbsp_place_holder;

9. class ExceptHook:

10. &nbsp_place_holder; &nbsp_place_holder;########################################################################

11. &nbspplace_holder; &nbsp_place_holder;def __init_(self, useSyslog = 1, useStderr = 0, emailRecipient = None):

12. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; self.useSyslog = useSyslog

13. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; self.useStderr = useStderr

14. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; self.useEmail = emailRecipient

15. &nbsp_place_holder;

16. &nbsp_place_holder;

17. &nbsp_place_holder; &nbsp_place_holder;#######################################

18. &nbspplace_holder; &nbsp_place_holder;def __call_(self, etype, evalue, etb):

19. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; import traceback, string

20. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; tb = traceback.format_exception(*(etype, evalue, etb))

21. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; tb = map(string.rstrip, tb)

22. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; tb = string.join(tb, '\n')

23. &nbsp_place_holder;

24. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; if self.useEmail:

25. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;emailFp = os.popen('/usr/sbin/sendmail -t -oi', 'w')

26. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;emailFp.write('To: %s\n' % self.useEmail)

27. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;emailFp.write('From: %s\n' % self.useEmail)

28. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;emailFp.write('Subject: Traceback notification from %s\n' %

29. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;os.path.basename(sys.argv[0]))

30. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;emailFp.write('\n')

31. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; else: emailFp = None

32. &nbsp_place_holder;

33. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; for line in string.split(tb, '\n'):

34. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;if emailFp: emailFp.write(line + '\n')

35. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;if self.useSyslog: syslog.syslog(line)

36. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;if self.useStderr: sys.stderr.write(line + '\n')

37. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; if emailFp: emailFp.close()

38. &nbsp_place_holder;

39. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; sys.stderr.write('Error in processing e-mail.\n')

40. &nbsp_place_holder;

41. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; # &nbsp_place_holder;TEMPFAIL causes the delivery to be retried

42. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; sys.exit(os.EX_TEMPFAIL)

43. &nbsp_place_holder;

45. &nbsp_place_holder;logging and exception handling

46. syslog.openlog(os.path.basename(sys.argv[0]), syslog.LOG_PID, syslog.LOG_MAIL)

47. sys.excepthook = ExceptHook(useSyslog = 1, useStderr = 0,

48. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; emailRecipient = 'user@example.com')

49. &nbsp_place_holder;

50. &nbsp_place_holder;parse the incoming message

51. (For Python versions <2.4)

52. import rfc822

53. headers = rfc822.Message(sys.stdin)

54. (For Python versions >= 2.4)

55. import email.parser

56. headers = email.parser.Parser().parse(sys.stdin)

57. &nbsp_place_holder;

58. &nbsp_place_holder;process the message here

59. syslog.syslog('Received mail from "%s", subject: "%s"' % (

60. &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; headers.get('From'), headers.get('Subject') ))

61. &nbsp_place_holder;

62. &nbsp_place_holder;demonstration of what happens when there's an error

63. &nbsp_place_holder;generate an error 50% of the time

64. if random.choice([ True, False ]): raise NotImplementedError('Test exception')

65. &nbsp_place_holder;

66. &nbsp_place_holder;successful return code

67. sys.exit(0)

comments powered by Disqus