As Evan said, your best bet is to have your PTR entry resolve back to your server's IP address.
However, if for some reason this is not possible, the PTR should suggest that you are using a statically allocated IP address, not a home (non-business) DSL line. As part of their anti-spam strategy, many organizations use reputation services (e.g., SORBS), which monitor IP address ranges for botnet activity and maintain blacklists of IP ranges. However, no matter of suspicious activity or not, they usually include their Dynamic User Lists (DULs) in their blacklist. To create these DULs, they use PTR records, and regular expressions, specifically tailored for the naming schemes of many large ISPs.
For example, a PTR like
cable-66-103-40-69.clarenville.dyn.personainc.net would be most likely automatically blacklisted (it matches "dyn", so it must be dynamic). There are some standardization efforts on reverse DNS naming in the IETF, with mixed success:
Slightly off topic, another source of information for black/whitelisting are WHOIS SWIP records.