resolving a blacklisted PHP Mail() IP

This post deals with Virtual Private Server e-mail settings, PHPbb forum, cpanel, and PHP Mail().
it may be outside the scope of vbforums.com and not sure where to ask it.
but i figure the friendly admin may step in to put it in it's right place (if there is one)
and i THINK it belongs here because it deals mostly with solving a PHP Mail() problem.

Alright, here's the deal -
mail sent from my php Mail() function appears to be blocked by many popular mail servers.

(an example from a yahoo reject i receive)

Code:

Delay reason: SMTP error from remote mail server after initial connection: host mta7.am0.yahoodns.net [66.196.118.240]: 421 4.7.1 [TS03] All messages from 173.212.241.74 will be permanently deferred; Retrying will NOT succeed. See http://postmaster.yahoo.com/421-ts03.html

Mail sent from PHPbb appears to also be blocked by these same pop servers:

(an example from hotmail reject i receive)

Code:

host mx3.hotmail.com [65.55.37.120]: 550 OU-001 (COL0-MC4-F41) Unfortunately, messages from 173.212.241.74 weren't sent. Please contact your Internet service provider since part of their network is on our block list. You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors.

BUT!!!
mail from my cpanel webmail account DOES go through (regardless of which cPanel webmail address is send from)

(header from successful yahoo receiver)

Code:

From WaxyStudios Wed May 8 21:22:07 2013 X-Apparently-To: [email protected] via 98.139.220.244; Thu, 09 May 2013 06:24:27 +0000 Return-Path: <[email protected]> Received-SPF: none (domain of waxystudios.com does not designate permitted sender hosts) X-YMailISG: tsOXHmMWLDvf0_49cOyJnDStWCXGy69IcQligG6qf.r0oI3n PIZQKIm0XjoR3krNuJoKGqkDNWPCZyiL_we8D2rDM8k3dml3vCcWYTbm3YX6 (....omitted for post...) JZCvwk8Oah94jlJKsqcyP7Y664CclmgMQiBjyw-- X-Originating-IP: [64.120.221.77] Authentication-Results: mta1153.mail.ne1.yahoo.com from=waxystudios.com; domainkeys=neutral (no sig); from=waxystudios.com; dkim=pass (ok) Received: from 127.0.0.1 (EHLO perfectionservers.com) (64.120.221.77) by mta1153.mail.ne1.yahoo.com with SMTP; Thu, 09 May 2013 06:24:26 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=waxystudios.com; s=default; h=Message-ID:References:In-Reply-To:Subject:To:From:Date:Content-Transfer-Encoding:Content-Type:MIME-Version; bh=g3zLYH4xKxcPrHOD18z9YfpQcnk/GaJedfustWU5uGs=; b=uj5zHqXqH5vTZWwCtTA+gebmaohFobvTtoF73sae480byt6V3QxpMU6oa/mhHe4frS5TCgruxYUd9FirtmH+JBHj+Sen6h1uybIdn+aM19DW+PoEmVbQtbSB86rgL+YrGXpBox/+oh1LXTwjWF3SO8JR0fLFvjTKVczwB48X1Fs=; Received: from localhost ([127.0.0.1]:41717 helo=waxystudios.com) by evo.webserverwelcome.com with esmtpa (Exim 4.80) (envelope-from <[email protected]>) id 1UaIMp-003F3j-Fi for [email protected]; Thu, 09 May 2013 00:22:07 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 09 May 2013 00:22:07 -0400 From: WaxyStudios <[email protected]> To: Waxy Studios <[email protected]> Subject: test In-Reply-To: <[email protected]> References: <[email protected]> Message-ID: <[email protected]> X-Sender: [email protected] User-Agent: Roundcube Webmail/0.8.5 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - evo.webserverwelcome.com X-AntiAbuse: Original Domain - yahoo.com X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - waxystudios.com X-Get-Message-Sender-Via: evo.webserverwelcome.com: authenticated_id: waxystud/from_h Content-Length: 5

(the only e-mails addresses contained in this post are related to my site, i'm not giving you any client information in this post.
and my ip address can easily be tracert'ed from any one looking at my signature so i'm not giving away anything there.)

So here's my question -
as with any standard VPS provider, i have full access to my cpanel directory.
what can i do to make my php mail() functions match my cpanel e-mail functions so that i'm sending my mail on the cpanel ip address?

Also - i have migrated my site about 3 weeks ago. it's possible that there is some kind of a php setting that i inadvertently transferred over
(but i honestly can't think of any - no php.ini , no .htaccess files transfered. and PHPbb ACP Server/Mail settings are configured for the new server)