<?php
$subject = 'abc dont@get.me 123 <input value="please@get.me">xyz';
$pattern = '/[A-Z0-9._%+-]+@[A-Z0-9.-]+.[A-Z]{2,}/i';
preg_match_all( $pattern, $subject, $matches );
var_dump( $matches );

array(1) { [0]=> array(2) {
    [0]=> string(11) "dont@get.me"
    [1]=> string(13) "please@get.me"
} }

array(1) { [0]=> array(1) {
    [0]=> string(13) "value="please@get.me""
} }

<?php
$subject = "<br data-xyz=please@get.me /> dont@get.me <[tag] [attr]='[pre] andPlease@get.me [ap]'>";
preg_match_all( $pattern, $subject, $matches );
var_dump( $matches );

array(1) { [0]=> array(2) {
    [0]=> string(13) "data-xyz=please@get.me"
    [1]=> string(13) "[attr]='[pre] andPlease@get.me [ap]'"
} }