Blocked by Verizon's anti-spam system - need assistance please

We've been getting the following block message and require de-listing assistance.  We've already submitted de-list request through the Whitelist form but have not yet received any response.

"571 Email from is currently blocked by Verizon Online's anti-spam system. The email sender or Email Service Provider may visit and request removal of the block. 141030"

Equally important, we'd like to understand exactly what specifically had caused the IP to be listed so that we can resolve the root cause of this listing.  Mailings are sent to subscribed non-profit members so the mailing behavior should not have constituted a block. 

Re: Blocked by Verizon's anti-spam system - need assistance please

Hi cwong,

Your issue has been escalated to a Verizon agent. Before the agent can begin assisting you, they will need to collect further information from you. Please go to your profile page for the forum and look at the top of the middle column where you will find an area titled "My Support Cases". You can reach your profile page by clicking on your name beside your post, or at the top left of this page underneath the title of the board.

Under "My Support Cases" you will find a link to the private board where you and the agent may exchange information. The title of your post is the link. This should be checked on a frequent basis, as the agent may be waiting for information from you before they can proceed with any actions. To ensure you know when they have responded to you, at the top of your support case there is a drop down menu for support case options. Open that and choose "subscribe". Please keep all correspondence regarding your issue in the private support portal.