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Background information:

I need to make a system that lets users log in by identifying themselves with an email address/password combination. So I'm trying to find a way to check that the login matches something in the database, when the two may be the same address that's typed differently.

So the initial steps for the domain verification are:

  • Convert the entered text to NFC
  • Strip comments with a recursive descent parser
  • split the local part from the domain.

  • run the domain through this:

    nslookup -type=mx $DOMAIN | awk '{ if($2 =="mail" && $3 == "exchanger") { print substr($6, 0, length($6)-1) } else if($2 == "internet" || $2 == "has") { print $1 } }' | sort | uniq'

    Which for both me.com and iCloud.com returns:

    mx1.mail.icloud.com
mx2.mail.icloud.com
mx3.mail.icloud.com
mx4.mail.icloud.com
mx5.mail.icloud.com
mx6.mail.icloud.com

    And gmail.com and googlemail.com both return:

    alt1.gmail-smtp-in.l.google.com
alt2.gmail-smtp-in.l.google.com
alt3.gmail-smtp-in.l.google.com
alt4.gmail-smtp-in.l.google.com
gmail-smtp-in.l.google.com

So I thought I would enter this into a table so that all the gmail servers have id 1, and all the iCloud servers have id 2, etc. in whatever order people try to register them in.

This doesn't work if all the servers are in one varchar unit, because servers could be added or removed at a later date. And it doesn't really work if the servers are all given their own row because there's no way to manipulate them as if they were a single logical unit.

If I get the longest common postfix of each server name would that indicate that these all use one mail server? or would it be possible for that to actually serve two servers separated by subdomains?

Patrick Jeeves
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  • What's going to happen when you get domains all pointing their MX records to a generic spam filter service, like Postini? – TessellatingHeckler Jun 21 '15 at 21:04
  • MX servers are also not static? and different domains can share the same mx servers (We currently have 400+ domains all pointing to our mail clusters and that doesn't count aliases such as (example.com / example.net / example.org). so I would be wary of trying to use mx records for anything ... – Doon Jun 21 '15 at 23:46

1 Answers1

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Though I have certainly learned a bit from your question, and I have seen question marks in it at the bottom, I will answer a different question at the bottom here.

But first,

Though you don’t have tags for the likes of php, you do mention the users are logging in, and a mysql database. So I am assuming php and not ssh.

You are not processing incoming emails and ripping thru smtp headers. Rather, grandma@gmail.com is typing that and not being cute by typing something else.

--

So the question is,

How do people login with an email address?

Just like every sane system. They enter it like grandma@gmail.com, password and you do your hashing and proceed.

Drew
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  • +1. OP seems to be operating on a flawed premise. If the part after the `@`, converted to lower case, is identical, they're the same domain. Otherwise, they're not. No exceptions. Common MX servers imply nothing, and different MX servers *also* imply nothing about whether the left hand side may route the the same mailbox. – Michael - sqlbot Jun 22 '15 at 02:27
  • I believe your point here, with which I agree, is this: the "your username is your email address" paradigm strips the bytes (or, maybe, the characters, if you feel generous) of the a given email address of any semantic meaning and transforms them into an opaque string that simply needs to be matched. – Michael - sqlbot Jun 22 '15 at 02:28