Salim Fadhley Salim Fadhley - 5 months ago 20x
Python Question

How do I validate the MX record for a domain in python?

I have a large number of email addresses to validate. Initially I parse them with a regexp to throw out the completely crazy ones. I'm left with the ones that look sensible but still might contain errors.

I want to find which addresses have valid domains, so given I want to know if it's even possible to send emails to .

I want to test that to see if it corresponds to a valid A or MX record - is there an easy way to do it using only Python standard library? I'd rather not add an additional dependency to my project just to support this feature.


There is no DNS interface in the standard library so you will either have to roll your own or use a third party library.

This is not a fast-changing concept though, so the external libraries are stable and well tested.

The one I've used successful for the same task as your question is PyDNS.

A very rough sketch of my code is something like this:

import DNS, smtplib

mx_hosts = DNS.mxlookup(hostname)

# Just doing the mxlookup might be enough for you,
# but do something like this to test for SMTP server
for mx in mx_hosts:
    smtp = smtplib.SMTP()
    #.. if this doesn't raise an exception it is a valid MX host...
    except smtplib.SMTPConnectError:
        continue # try the next MX server in list

Another library that might be better/faster than PyDNS is dnsmodule although it looks like it hasn't had any activity since 2002, compared to PyDNS last update in August 2008.

Edit: I would also like to point out that email addresses can't be easily parsed with a regexp. You are better off using the parseaddr() function in the standard library email.utils module (see my answer to this question for example).