In my experience, bureaux and AS vendors will speak to customers but are frequently unwilling to speak to other senders. In that situation the best solution is to find a recipient who isn't receiving your mail and persuade them pretty-please to put a call in for you as the commercial boot is on their foot.
A problem from a badly-configured system should show up on multiple lists, not just one. From memory, older Barracuda appliances have a problem if the sender has harsh SPF (terminating -all) and the appliance is on a relay of some sort, as they do a quasi-SPF check that isn't terribly obvious and can't handle Incoming Relays the way Asyncos can. This will be compounded by the fact that the recipient should have realised there was a general problem but hasn't.
Failing that the OP has a commercial profile where the majority of the recipients are Barracudas (!) so their list screams first. In that case check the monitor graphs for internal users sending bulk and possible backscatter from anti-virus or content rules.
