said by beejay1 :

So why was Insight blacklisted in the first place? Could it have anything to do with this:

WARNING: One or more of your mailservers is claiming to be a host other than what it really is (the SMTP greeting should be a 3-digit code, followed by a space or a dash, then the host name). If your mailserver sends out E-mail using this domain in its EHLO or HELO, your E-mail might get blocked by anti-spam software. This is also a technical violation of RFC821 4.3 (and RFC2821 4.3.1). Note that the hostname given in the SMTP greeting should have an A record pointing back to the same server. Note that this one test may use a cached DNS record.

gateway.insightbb.com claims to be non-existent host asav03.manage.insightbb.com:
220 asav03.manage.insightbb.com ESMTP