I need the header data ["in-reply-to:"] =>, for keeping track of the acknowledgment. When I send the email I keep the email id and so then corresponds exactly to that email acknowledgment.
I've seen it with var_dump ($ decoded  ['Headers']); does not always get the data ["in-reply-to:"], however if I go into the email if the original data-Message-ID: <eb592ea2163ebde84959c1677f4913e1@domain> which is where I think you get the value.
Manuel Lemos - 2013-04-16 09:18:44 - In reply to message 1 from Silvia
I think the problem is that you are trying to display the decode structure in a Web page and if you do not encode the values, browsers will consider anything between < and > as a tag, so you may not see anything in the browser but it is there if you check the page source code.
You need to use HtmlSpecialChars function to properly display the value in a Web page.
Manuel Lemos - 2013-04-17 03:45:57 - In reply to message 3 from Silvia
I think I did not explain myself clearly. HtmlSpecialChars is not to make emails appear in that header. If the emails are in the message, the emails appear in the decoded array.
The problem is that if you just use var_dump to show the array contents, that function is not be suitable to display the message structure in a Web page because all text needs to be encoded to show in a HTML page, especially if the array has values with the characters <, > or " .