The Roller Network operates several mail services, including a Secondary MX service and SMTP Redirection service. All of our filtering options are highly customizable, and as such, there are many possible combinations of filtering. A message may have been rejected or deferred by a Roller Network server for any number of reasons. A rejection or deferment of a message is the result of a filtering option configured by an account holder, not the Roller Network itself.
We (Roller Network LLC) do not control filtering for our customers. If you have a problem with a customer's email filtering policies please contact them directly through alternative means. Our staff cannot interfere with a customer's chosen filtering policies.
Some specific points of our mail services:
• A 451 "Deferred" SMTP response. This is not necessary a fatal message or an indication of the status of the remote site. Some of the filtering options will return a deferred message in the SMTP session explicitly; most notably the Greylisting filter.
• Our Greylisting filter will always return a generic 451 deferred message if the message does not pass the greylisting filter tests. The Roller Network SMTP servers will not explicitly reveal the Greylisting filter. For a detailed look at how greylisting works, read Evan Harris' whitepaper The Next Step in the Spam Control War: Greylisting and other information at greylisting.org.
• Some filters can be configured to perform their tests, but accept the message and add a header tag of the result for further filtering or scoring once it leaves our system and is processed by the final destination server. In these cases, the customer may decide to ultimately discard or file the message in a "spam" folder even though our services indicated it as accepted.
• Any filtering that is performed by the Roller Network SMTP servers is performed in real time during the SMTP session. With the exception of header tagging, the SMTP session responses are the final result of a message being processed by our filters. We do not perform any after-queue filtering or inspection; it is simply passed along to the final destination or routed in whatever manner the customer has specified.
The "postmaster" and "abuse" Addresses
The "postmaster" and "abuse" addresses are required by the RFCs to be usable. Although it is possible the message may still be discarded by the recipient, the Roller Network will not filter those addresses. An "abuse" address is required by RFC2142, while "postmaster" is required by RFC2821 section 4.5.1.
In the event that "postmaster" or "abuse" are not functional, we recommend trying other well-known administrative addresses such as "admin" or "webmaster".