DoD contact

Can anyone recommend a preferred method for contacting the network folks at the DoD ? It seems they blanket banned large swaths of our upstream provider ( Aptum AS 13768 ) which includes all of our subnets as well. We can't connect to any IP that they manage which includes DNS resolution for .mil , mail service, etc. I tried reaching out ( and Aptum as well ) to disa.columbus.ns.mbx.hostmaster-dod-nic@mail.mil  from an external address and although the e-mail didn't bounce, we also didn't receive any answer for a few days now. Is there another way to get in touch with them ? Thanks! Scott