Verify the domain of an e-mail address

Question

I am writing a Python script that checks the inbox of an IMAP account, reads in those e-mails, and replies to specific e-mails. However, for security reasons I need to make sure that the original sender of the e-mail came from a particular domain.

I am reading the e-mails in Python using the email library and its message_from_string function:

msg = email.message_from_string(data[0][1])

This gives me easy access to the sender via msg['from']. After some testing, I've found that this is generally in the format John Doe <JohnDoe@example.com> but I would think it could also be in the format JohnDoe@example.com.

As I said, I want to make sure the domain of the sender's e-mail is, say, foobar.net. What would be the best way to verify that? Should I use a regex so I can pull out the e-mail regardless what format msg['from'] is in? Or should I just do a string split on @ and then check the next 10 characters are foobar.net? Something else entirely?

Answer 1

I'm really not a fan of the regex option, especially as so many people commented on answers here, it is very hard to catch all cases.

Instead, I decided to use the Python email.utils.parseaddr function which will split the message "From" header to a tuple of (name, addr). From there, using addr.split('@') will split the e-mail address into its local part and domain part, and I can match the latter against the domain I'm verifying for.

So, the answer to my question is:

msg = email.message_from_string(data[0][1])
addr = email.utils.parseaddr(msg['From'])[1]
domain = addr.split('@')[1]
if domain == "example.com":
    print "Verified requester"

Answer 2

I'd definitely recommend to use a regex. However, you should also be aware that the 'from' field in emails is set by the email client and can be spoofed without much effort. So you should think if maybe also checking for the sending mail server might be an option.

Cheers Hendrik

Answer 3

Doesn't the email library have functions to extract a sender and their domain?

But if it doesn't, and if it's just one, known domain you want to check for, just check if the msg['from'] contains @foobar.net and be done with it.

Answer 4

You could try this pattern for simple domains:

PATTERN

(?<=@)\w+(\.\w+?)+?(?=>)

This pattern basically will check everything after @ and before >

INPUT

1. John Doe <JohnDoe@example.com.no>
2. John Doe <JohnDoe@foobar.net>

OUTPUT

1. example.com.no
2. foobar.net

As mentioned in the comment you could use some sort of contains method, then I googled a bit for it and if you know the domain you could use something like this:

PYTHON CODE

if "@foobar.net" in msg['from']: continue

This code is basing on:

stackoverflow.com

Answer 5

import re
email = 'JohnDoe@example.com'
re.search(r'@((\w+?\.)+\w+)', email).group(1)

Note:

As given at here, correct regex to match email address is:

(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t] )+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?: \r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:( ?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\0 31]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\ ](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+ (?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?: (?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z |(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n) ?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\ r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n) ?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t] )*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])* )(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t] )+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*) *:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+ |\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r \n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?: \r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t ]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031 ]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\]( ?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(? :(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(? :\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(? :(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)? 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Wow!!