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Question

Regular expression to match free email accounts

Answer 1

+1 A:

/\@(hotmail|yahoo|gmail)\.com/

stillstanding 2010-02-23 13:04:37

Answer 2

A:

Have you tried a big ol' disjunction?

i.e.

yahoo\.com|googlemail\.com|blah\.net

Pros: Easy to build, easy to read, explicit.

Cons: Maybe not the most efficient mechanism.

Brabster 2010-02-23 13:05:25

Actually if it were using Perl v5.10 it would be very efficient. That's because it becomes a trie.

Brad Gilbert 2010-02-25 16:51:25

Hmmm, not come across a 'trie' before - very interesting, thanks for the comment!!

Brabster 2010-02-25 18:28:25

Answer 3

A:

regex would be sth like:

[a-zA-Z0-9_\.+]+@(gmail|yahoo|hotmail)(\.[a-z]{2,3}){1,2}

you can add all the other domains you want... does it help you?

PierrOz 2010-02-23 13:06:21

Obviously, the trick is how to get the list of 'all the other domains'.

Tadeusz A. Kadłubowski 2010-02-23 13:13:18

This worked first time, thanks for all the answers

2010-02-23 13:17:09

Can't vote up as I'm new :-)

2010-02-23 13:17:35

@hixster, you *can* accept an answer, can't you? EDIT: I voted up your question, so now you have enough points to up-vote anyone.

Bart Kiers 2010-02-23 13:20:48

Cool, accepted.. Thanks again!

2010-02-23 13:24:47

-1: `[email protected]` and I pass through your regular expression as using a paid service. Please people, don't forget `+` is a valid character in an email address.

Andrew Moore 2010-02-23 13:42:03

Also, [email protected] is a valid alias for [email protected], so this will pass through the above regex as well.

prometheus 2010-02-23 14:02:11

@prometheus: `.co.uk` addresses are properly parsed by the above regex. Notice the `(\.[a-z]{2,3}){1,2}`... (dot)(2 to 3 letters)(repeated 1 or twice).

Andrew Moore 2010-02-23 14:10:42

O.K how do I prevent .co.uk getting though as well?

2010-02-23 14:13:13

@Andrew, so what about [email protected]? And so on ...

prometheus 2010-02-23 14:32:48

@Tadeusz: I'm not sure you can find the domains automatically without a config list or sth like that. At least, I thought the question was more about the regex (cf. tag)@Andrew: my bad... but the -1 is tough, sniff... :(

PierrOz 2010-02-23 15:11:32

@hixster: haha, that's a slippery slope I mentioned before. You'll be worrying about free email in Paraguay just after dealing with UK. This problem cannot be solved reliably. How much money is your client willing to sink in annoying gmail users that might want to deal with the system?

Tadeusz A. Kadłubowski 2010-02-23 15:15:10

@PierrOz: Exactly, there must be some manually created config list. And the config list always will be incomplete. An incomplete solution to a pointless problem specified by some Pointy-Haired-Boss.

Tadeusz A. Kadłubowski 2010-02-23 15:17:42

@PierrOz: fact is, you don't even need to check what's before the @... Personally, I would simply go for `@(yahoo|google|hotmail)(\.[a-z]+)+$`

Andrew Moore 2010-02-23 19:22:51

i'd drop the `(\.[a-z]+)` and change the entire expression to a simple `/\@(yahoo|google|hotmail)\./` so it can catch `.co.uk`

stillstanding 2010-02-23 21:13:42

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Regular expression to match free email accounts

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