--- /dev/null
+--TEST--
+Bug #20273 Mail_mimePart::encodeHeader() and TAB character
+--SKIPIF--
+--FILE--
+<?php
+include("Mail/mimePart.php");
+
+$refs = "<test@domain.tld>\t<test2@domain.tld>";
+$mime = new Mail_mimePart();
+echo $mime->encodeHeader('References', $refs);
+?>
+--EXPECT--
+<test@domain.tld> <test2@domain.tld>