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Editorial Team
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Asked: 2026-05-24T00:44:42+00:00

I try to match email addresses but only when they are not preceeded with

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I try to match email addresses but only when they are not preceeded with “mailto:”. I try this regular expression:

"/(?<!mailto:)[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,4})/"

against this string:
'<a href="mailto:someemail@domain.com">EMAIL</a> ... otheremail@domain.com '

I would expect to catch only 'otheremail@domain.com', but I also receive 'omeemail@domain.com' – see missing 's'. I wonder what’s wrong here. Can’t I have a normal regex after the lookbehind assertion?

My whole example in PHP looks like:

$testString = '<a href="mailto:someemail@domain.com">EMAIL</a>  ...   otheremail@domain.com ';
$pattern = "/(?<!mailto:)[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,4})/";
preg_match_all($pattern, $testString, $matches);
echo('<pre>');print_r($matches);echo('</pre>');

Thank you!

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1 Answer

  1. Editorial Team

    Because after s there is a string that matches your regex, omeemail@domain.com, and because s is hardly mailto: it matches. Getting a word boundary in there will work for most cases:

    Change:

    (?<!mailto:)

    To:

    (?<!mailto:)\b

    On a side note: use example.com for examples, domain.com is owned by an actual company.

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