Email Troubles - PTR needed?

On-Premises Exchange server.  Was using outbound filtering from Intel / McAfee and have now switched services.  For other reasons we cannot use the new smarthost so now sending mail directly from Exchange.  A few domains (Hotmail / Comcast and possibly others I am so far unaware of) seem to accept the mail but never deliver.  Have checked SPF settngs and they seem correct so was wondering if a PTR record would do the trick.

Thanks in advance!