Vtiger outgoing mass email problem -- 2

Using vtiger and PHPlist (bulk emails are sent via a PHPlist plugin, but only when a campaign is created in VT). Emails show sent in Vtiger but contacts are not getting the emails. Single emails get sent by VT but mass are not getting thru (use VT list view to send out to max 100 contacts, if more then it is piped thru the PHPList).
Mass emails via VT or PHPList are not going thru (as mentioned single emails are getting thru).

Site is a live site hosted on a shared server (cpanel) .. prefer to work via teamviewer and cannot share login info.