We had an issue where we sent a delivery failure to a SORBS Spam Trap address. This may be the case with you too. They will de-list without fees if this is the case. It took a bit to get it done but once we got a response from someone they were very responsive.
When I was first building up my network I hadn't set reverse dns away from what my colo gives. So the PTR record for my sending IP looked like:
SORBS decided that looked like a DSL address and threw me into the bucket of blacklisted dynamic senders. Then my network provider (sorbs wouldn't talk to me) spent the next month working with them to get delisted. Absolutely ridiculous, I wish email adminstrators would stop blocking email based solely on these silly blacklists.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...