$re = '/"SenderAddress":"\w+.*@(?<s_domain>.*)","RecipientAddress":"\w+.*@(?<r_domain>\S+)\w+/m';
$str = '{"EventReceivedTime":"2019-06-26 09:47:53","SourceModuleName":"EXCHGETMESGTRACEPRD","SourceModuleType":"im_file","MessageId":"<0100016b93ffa54d-a8a96a78-94b0-46e6-aed6-c0e82ef6d228-000000@email.amazonses.com>","Received":"6/26/2019 9:35:33 AM","SenderAddress":"DoNotReply@ConnectedCommunity.org","RecipientAddress":"jfz5@blah.edu","Status":"Delivered","Size":"0"}';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php