I recently built a mail server for a client. It went as smoothly as it could have . . .
until I started getting reports of delays and undeliverables from AOL addresses and Juno addresses. I had forgotten to set up a reverse DNS entry. Frankly, I think a reverse DNS entry (PTR entry) is a meaningless way to address spam issues - but what can you do?
Someone seriously needs to take the lead and start enforcing SPF records. Anyway, don't forget to create reverse DNS entries. And in case anyone other than me ever reads this blog - a reverse DNS entry is created by your ISP - not your DNS host.